Very useful for my job as a support tech where I need to paste the same text into ticket updates frequently.

I also use it to paste BBCode formatting elements into ticket updates, so a handy feature would be to use the currently selected text as a preset to use in a placeholder.

For example I could have clipping that contains "[CODE]$[SELECTED][/CODE]". I could then select some text in a form field, then hit the shortcut key for this clipping, and it would wrap the selected text in BBCode CODE tags. I don't know if Firefox would allow accessing selected text in this way though.