This is one of the things that will hopefully be solved any day now™ by the addition of a hook system - quote from an older PM:
I’m currently working on a generic “hook hotkey” feature (maybe assigned to Ctrl-!). The rough idea is that it would pop up a dmenu window where e.g.
foo bar bazcan be entered to launch the command~/.local/share/split-browser/hooks/foo 'bar baz'with […]$SB_URLand$SB_TITLEof the active tab.
For example, an included hook could unbookmark the active tab’s URL (after confirmation).