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

Thunderbird, Postbox

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

Reset Zoom

Reset Text Size

Reset Text Size to the default setting.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Copy

Copy Selected Text

Copy selected text.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Toggle menu bar

Toggle the menu bar

Toggle the menu bar. Don't put this button on the menu bar!

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Import

Import Settings and Data

Import settings and data from another application.

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

Hide Toolbars

Toggle visibility of all toolbars, except the main toolbar

Toggle the visibility of all toolbar, other then the main toolbar.

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

Page Fonts

Toggle between the default and the sites fonts

Toggle between the use of the fonts used by the site and those that are set as the default.

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