Numbers Format/Add Link options are greyed out

Numbers Format/Add Link options are greyed out

Trying to create a Table of Contents tab so I can easily get to a tab buried in the set. I read a post about the Add Link options greying out dated 2012. It is currently almost 2021. The writer said you had to change your options to rich text. That's quite a long time ago and rich text options are nowhere to be found. I think everything is rich text these days. So I don't see any option for fixing this using that method. Does anyone have any suggestions?

I am running MacOS Catalina 10/.15.7 and Numbers 10.2.