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

Thunderbird, Postbox

Paste

Paste

Paste text.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Select All

Select All Text

Select all the text in the current text box, web page, etc.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Tools Menu

Show the tools menu

Show the tools menu.

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

Edit Menu

Show the edit menu

Show the edit menu.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Languages

Open Language Manager

Open the Language Manager to enable or disable or do any other needed tasks to any of your language packs.

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

Update

Check For Updates

Check for updates to the currently open application.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Cookie Exceptions

Open the Cookie Exceptions dialog

Open the cookie exceptions dialog.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey

Get Extensions

Get more Thunderbird extensions

Open addons.mozilla.org on the page to get more Thunderbird extensions. Link can be change using about:config if you prefer another site.

Compatibility: Pale Moon Thunderbird, Postbox SeaMonkey