Great game and much fun to play!
I noticed a few very small details that could be improved in my opinion:

• There is no sound anymore when after the (sometimes rather long) search for an enemie finally an opponent has been found. Sometimes I am playing Steem Monsters beside doing other things, and thus unintentionally forget to start the match ... If there was a reminding sound, that would happen less often.

• After I have clicked "Make Team" I don't see the name and the last teams of my opponent anymore, but sometimes I clicked too fast (or my memory is too weak) so that it would be really useful still to see the data of the opponent while building ones team.

• If I have chosen a summoner and a splinter, but then decide to change the splinter, I cannot choose the same splinter together with this summoner again (first I must choose another splinter and then the old splinter again - which costs quite some time).
  Of course it sounds illogical to choose the same summoner and splinter again after one actually wanted to change it, but under time pressure it sometimes happens to change ones opinion several times. Then it can be annyoing (so time consuming) if not every option is available immediately.