Hello @Per5 

No such OOTB shortcut available to switch between tabs in workspace, only to highlight tab there is shortcut present which is "Control+Alt+2 OR Command+Option+2"

You can find ootb shortcuts available on below links:
https://www.servicenow.com/docs/csh?topicname=next-experience-keyboard-shortcuts.html&version=latest

https://www.servicenow.com/docs/csh?topicname=r_KeyboardShortcuts.html&version=latest

If my response has helped you hit helpful button and if your concern is solved do mark my response as correct.

Thanks & Regards
Viraj Hudlikar.