Simple Commands for changing Gamemodes! The PLugin is for the 1.12.2
Gamemode Creative: /gmc or /gmc >player< Perm: simple.gamemode.gmc
Gamemode Survival: /gms or /gms >player< Perm: simple.gamemode.gms
Gamemode Adventure: /gma or /gma >player< Perm: simple.gamemode.gma
Gamemode Spectator: /gmsp or /gmsp >player< Perm: simple.gamemode.gmsp