I tried many options and settled on this:
One Lookup Group Data Table:
One Lookup Data Table:
The resulting Page Table:
This way the User can add/edit new Lookup Groups and Lookups easily.
I always use Row IDs, which allows the User to edit the Name with breaking the Relation.
I know that this uses some more Rows but prefer it over this way which is prone to mistakes and only useful when the User has direct access to the Data Editor:
I actually asked for a new Feature eliminating these Tables but it seems that there is no interest:
https://community.glideapps.com/t/use-choice-component-as-combobox/54265