Can I merge several state.dats to one?
Yes. Rename another state.dat to merge.dat and open Elma (so you have one state.dat and one merge.dat in your Elma directory). After quitting the game you have times merged to state.dat but note that the program doesn’t understand same times. So if you have same times in top10 in one or both of the state.dats they’ll get messed up, only one of them will stay. This is a bug and should be fixed in the next versions of the game. After merging you can remove the merge.dat.