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

Thunderbird, Postbox

about:config

Open about:config to change settings

Open about:config to change hidden settings that cannot be edited from the Options window.

All Mozilla based programs have settings that can not be changed in the options window. These hidden settings are all reveled in the about:config where anything can be changed or reset.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Toggle Proxy

Toggle The Proxy On & Off

Toggles the Proxy between on and off for quick changing of networks.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Add-ons

Open Add-ons Manager

Opens the Add-ons window to perform tasks on your installed Extensions, Themes, Plug-ins and Language packs.

The Add-on's window allows the installation and management of all your extensions and themes. If you need an update, change a setting, swap themes or enable/disable an add-on the Add-ons' window is the place to go. Being able to access this quickly is a necessity for anyone that uses even a handful of add-ons.

The button also contains a drop down menu that allows you to install add-ons, open the add-ons window to the extension or themes tab, or set which websites can install addons.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Undo

Undo Last Change

Undo last change/action.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Work Offline

Toggle work offline

Toggle Work Offline and Work Online.

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

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

Zoom In

Enlarge Text Size

Enlarge the text size on sites that makes the text so small you can't read it.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Zoom Out

Reduce Text Size

Reduce the text size so it is not so big.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Print Preview

Open Print Preview

Open the Print Preview to view a page before printing it.

Paper costs money (and trees) so it is worth checking what the page looks like before you print it. Though it has always amazed me just how much the button gets downloaded.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey