Here are some Firefox (and forks*) keyboard shortcuts I did not know about/keep forgetting:
Shift+Space up a screen
Alt+MouseDrag select link text only
Ctrl+Shift+PageUp move tab left
Ctrl+Shift+PageDown move tab right
Ctrl+Shift+N reopen last closed window
Shift+Delete delete selected autocomplete entry
Shift+Enter open focused link in new window
Ctrl+Enter open focused link in new background tab
Ctrl+Shift+Enter open focused link in new tab
Ctrl+M mute
Ctrl+Alt+R reader mode
Ctrl+Shift+I toggle developer tools
Ctrl+Shift+K developer tools console
Ctrl+Shift+E developer tools network
Ctrl+Shift+J browser console
In search bar:
Alt+Enter open URL/search in new tab
Alt+Shift+Enter open URL/search in new background tab
Shift+Enter open URL/search in new window
This brought to you by my pointless hope that one day the people at Mozilla will put me out of my misery and provide an alternative binding for F6
* In all likelihood. While I did not check, I can say that at least LibreWolf has them unchanged