These are a ready make selection of some of the most popular buttons from the Custom Toolbar Button Maker

Thunderbird, Postbox

Menu

All menus

Show all the menus in a single menu.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Source

View Page Source

View the page or message source code.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Zoom Text Only

Toggle between text and page zoom.

Toggle between text and page zoom.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Add-on Preferences

Open the preference window of an add-on.

Displays a submenu that allows you to open the option window for any add-on that has one.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Plugins

Open Plugin Manager

Open the Plugin Manager to enable or disable or do any other needed tasks to any of your plugins.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Save

Save document as

Save the currently open document, or image to a file.

Saving a page or email for later viewing or to send to a friend is a much needed functionality, so much so that there really should be a toolbar button for it.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

about:plugins

Open about:plugins to view installed plugins

Open about:plugins to view installed plug-ins.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Codefisher

Open Codefisher.org

Opens various pages of the Codefisher.org website.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Copy

Copy Selected Text

Copy selected text.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Exit

Exit Application

This button not only closes the current window, but every one that the current application may have open. It is a lot quicker than finding all windows and closing them one at a time.

Finished browsing or reading all your emails, left lots of windows open? Don't want to have to shut them all one at a time? This little button can close them all, with out you having to do it all.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey