For more information on current test or beta released visit the MozillaZine site here

So what does this puppy do? The primary goal of this extension is to provide the tools needed to install and manage extensions and themes locally. To do this the extension provides multi-extension installation support, hacking capabilities to the Extension/Theme manager windows, features to find and troubleshoot Extensions/Themes Build, GUID and Profile information.

** Please read the special note #1 before installing or upgrading to take advantage of the full power of this extension. **

Feature list below has not been fully updated for 4.0 release, update coming soon.

Extension & Theme Managers

• Install buttons to both the Theme & Extension Manager to match the Thunderbird/NVU interface *
• New menu to top of window with several options like (with option to hide the whole menu):
  Install Extensions/Themes, Config Export, Disable/Enable All Extensions, Manually Sort list, Edit My Config, Restart and a Links menu
• Multi-extension installation support, just hold the ctrl, cmd or shift keys to select multiple XPI's
• Extension/Theme enabled/disabled count to manager window
• "Browse Install Directory" to right-click context menu for Extensions & Themes
• "Copy GUID" to right-click context menu for Extensions & Themes
• Slim mode option to Extension & Theme manager listings, on by default *
• Sort Extension & Theme lists option, off by default *
• Slider for Theme manager to resize list and preview pane
• Option to show the Theme Preview image below the Themes list
• "My Config" icon to the main menu
• EM or TM icon to the main menu to allowing switching between windows
• "Restart" icon to the main menu
• Option to disable the XPI install time delay on the Extension install prompt, on by default
• Remembers separate install paths, one for Themes and one for Extensions
• Options to show/hide manager elements like:
  "Get More..." link, Theme Manager Preview, Button Bar, Button images, Context menu options
• Option to show Extension/Theme manager window in: New Window, New Tab, Current Tab/Window or Sidebar
• Temporarily enables XPI install preference to get local XPI's to install and then sets it back to previous state.

File, Tools & Help Menu

• "Copy userAgent/Build Id" options to Tools menu *
• "My Config" export options to Tools menu *
• "Edit My Config" option to Tools menu *
• "Get More Extensions" and "Get More Themes" options to Help menu
• "About:?" submenu with shortcut to about:config & several other about: options to Help menu
• "Install Extensions" & "Install Themes" options to the File Menu with Alt-X Shortcut & Alt-M Shortcut keys - check Options dialog to hide *
• Ctrl-Shift-E Shortcut Key to "Tools|Extensions" menu *
• Ctrl-Shift-T Shortcut Key to "Tools|Themes" menu *
• Alt-O shortcut to "Tools|Options..." menu *
• Options to always show Mozilla Update icon on toolbar (only works with Fx/TB 1.0.x builds).
• Options to show/hide new "Local Install" File, Tools & Help menu options

Toolbar Buttons

• "Extensions" & "Themes" buttons with extended context menu options *
  New feature include button drops, for Extensions the drop down will show Extensions with Options or preferences, for Themes dropdown it will allow you to switch you theme (switching themes will prompt to restart on 1.5 build, prompting can be turned off in Options panel).
• "about:config" button to open the about:config configuration page, with context menu of all available about: options.
• "about:plugins" button to open the about:plugins information page, with context menu of all available about: options.
• "Build ID" button to allow pasting of User Agent and Build ID information to text or input box.
• "Clear Cache" button to clear the disk and memory cache.
• "Clear Private Data" button to clear or prompt on what to clear based on the new Firefox 1.5 Privacy options
• "Edit My Config" dropdown menu button with several profile and browser core file editing features.
• "JS Console" button to open the JavaScript Console window.
• "My Config" button that displays your current configuration with options to save to text, html or bbcode. *
• "Options" button to open the Options dialog.
• "Restart" button to restart the current app with option to prompt in preferences (only work with Fx/TB 1.5 and above).
• "Get All" button for Thunderbird to get all mail and send unsent mail.
• "Toggle Preview" button for Thunderbird to toggle the preview pane.

Other Tools

• Customized Title options to display internal application variables to main window title. *
• "Paste userAgent/Build ID" to input and textarea boxes context menu.
• "Archive XPI" and "Archive JAR" context menu option fro xpi & jar file downloading.
• Option to Auto-Archive Extensions & Themes on installs (archiving on updates currently only works with 1.0 builds)

Options & Other Goods

• Enable/disable Extension Installation and access to Installation "Allowed Sites" from Option dialog
• Options to manually edit the default Extensions & Themes file dialog install paths
• Options to disable File or Tools menu options and shortcuts
• Adds Esc key to close View Source window
• Remembers JS Console window size
• Remembers DOM Inspector window size and allows Esc key to close window
• Theme supported button icons *

Special Notes:
1) The following extensions can be disabled or uninstalled if you have version 4.5.2 or newer installed (auto uninstall check will prompt you when you first open the extension manager after installing 4.5.2 or newer):

1. About [Button]
2. AboutConfig (Thunderbird 1.5 or newer)
3. About:Config (ff) by Sonny Piers (pitux)
4. About:Config (Sunbird)
5. about:kitchensink
6. AboutPlug
7. Add-ons Sidebar
8. Browse Extension
9. ChromEdit
10. ChromEdit 2
11. ChromEdit Plus
12. Config Files Editor
13. Clear Cache Button
14. Clear Private Data... (Add-Ons)
15. Close All Child Windows
16. Disallow XPInstall
17. EMButtons: Firefox & Thunderbird
18. Edit Config Files
19. Ext2Abc
20. Ext2File
21. Extension List Dumper
22. Get All Mail
23. HideUpdate
24. Install New Theme
25. ListZilla
26. MR Tech's About:About
27. MR Tech's Disable XPI Delay
28. MR Tech's Toggle Preview Pane
29. Nightly Tester Tools Lite
30. Open Profile Folder
31. Option Menu
32. Options Toolbar
33. Profile Folder
34. QuickRestart
35. Restart Firefox
36. Restart Thunderbird
37. Sanitize
38. Show Extension Directory
39. Show Failed URL (for Firefox 1.0.x based browser)
40. Simple Add-ons Button
41. Simple Clear Button
42. Simple EMbuttons
43. Simple Options Button
44. Slim Extension List
45. Sort Extensions
46. Throbber Button
47. Toggle Preview Pane

2) Access Keys may be different based on language localization changes

3) To add a new translation or to update an existing one you can download and modify the local_install.ent, local_install.properties, about_about.dtd, disable_xpi_delay.properties and the contents.rdf files here, then email them with the proper language code (ie:fr-FR, etc) to mrtech [at] gmail.com

4) To add theme support, just add formatting for the "installNewTheme" id, which is used for both the extension & theme buttons. Currently works with Default theme, both Doodles, Aaron Spuler's themes & Mostly Crystal. Note: "installNewTheme" was the original id from the "Install New Theme" extension and already had some theme support out there so I decided to keep it for both manager windows.
To remove image from your theme just use:
#installNewTheme > hbox > image { display: none !important; }

Localizations include: cs-CZ, da-DK, de-DE, en-US, es-AR, es-ES, fi-FI, fr-FR, hr-HR, hu-HU, it-IT, ja, ko-KR, mk-MK, nl-NL, pl-PL, pt-BR, ro-RO, ru-RU, sk, sr-YU, zh-CN, zh-TW

Contributors:

• Bradley Chapman: This extension's roots started with "Install New Theme".
  
• Tom Kuter (Evolic): Install Button graphic
• Andrea: Italian Locale (it-IT) Localization
• Frackounet: French (fr-FR) Localization
• Duriel: Simplified Chinese (zh-CN) Localization
• Leszek(teo)Zyczkowski: Polish (pl-PL) Localization
• Fernando Pereira Silveira: Brazilian Portuguese (pt-BR) Localization
• Armin C. Schneider: Germany (de-DE) Localization
• Peter TC: Traditional Chinese (zh-TW) Localization
• Alf: Dutch-Netherlands (nl-NL) Localization
• Henriett Peller: Hungarian (hu-HU) Localization
• Ljubisa Radovanovic: Serbian (sr-YU) Localization
• Mihai Capota: Romanian (ro-RO) Localization
• Josef Kotva: Czech (cs-CZ) Localization
• Masaaki Matsuyama: Japanese (ja-JP) Localization
• Proyecto Nave: Spanish (es-ES) Localization
• Akilles : Finish (fi-FI) Localization
• Quicksilver tears : Russian (ru-RU) Localization
• Flactal : Korean (ko-KR) Localization
• SlovakSoft: Slovak (sk) Localization