These are a ready make selection of some of the most popular buttons from the Custom Toolbar Button Maker
Thunderbird, Postbox
Select All
Select all the text in the current text box, web page, etc.
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
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
Menu
Show all the menus in a single menu.
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
Toggle menu bar
Toggle the menu bar. Don't put this button on the menu bar!
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
Free Memory
Free unused memory that Firefox is currently using.
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
Undo
Undo last change/action.
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
Work Offline
Toggle Work Offline and Work Online.
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
Redo
Redo the late change.
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
about:about
Lists all the "about" pages so that they can be opened.
Compatibility:
Pale Moon
Thunderbird, Postbox
SeaMonkey
about:config
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