I'm not sure if this is a feature or technical issue:
A few days ago I hit the max Lvl for the first time. But I was surprised, that it didn't tell me that I reached the max lvl. The upgrade button still showed me the costs, but remained grey and unclickable.
Later on mobile I realised that it actually says "Max".

Would like to see the "Max" also on my Desktop.

PS: I'm playing on Steam.