Multiple choice switch

I’ve been reading up on switches but as far as i can gather the switch function is most often on/off.
What i want to do is a multiple choice switch. In the end i’d ideally like a drop-down menu or something alike that lets me choose the operating mode of a genset. The modes are available in a modbus holding register with values; 0 - Off, 1 - Manual, 2 - Auto, 3 - Test. So a button labelled with a readback would be ideal. I’m thinking this should be rather simple but my google-fu isn’t working.
How can i get this done?

With some modification this could work too:

I guess i’m in over my head here. Trying the input select method but i can’t change platforms from mqtt to modbus "Value not accepted. Valid values: “mqtt”, if i’m even supposed to do that.
How should the input select interact with the modbus register specified? I guess that’s done via an automation, but since the editor won’t let me choose i don’t know how to go forward.
Somewhere i need to associate numerical values to text labels also, which i’m guessing mqtt doesn’t need?