Paste on Top Keyboard Shortcut

Glad to see paste on top back, is there a keyboard shortcut as I use this a lot to copy text labels to multiple images

There isn’t otherwise you’d see it (b34). Unfortunately it’s not a main menu item so you cannot customise your own shortcut via Mac OS Preferences.
On1 Photo Raw recently added the ability to add and change shortcuts within the app itself. Perhaps you should request this, although I doubt whether it will come in FM v6!