Custom variables

It would be great to be able to save custom variables (even if they are only strings) (EX. ActiveAdmins = @a[tag=Admin] //would be whatever the return value of @a is.) and use them in other commands, such as tellraw (EX. tellraw @r {"rawtext":[{"text":"available mini games are %s. Closed mini games are %s".format(IMyOpenGames, IMyClosedGames)}]} ). And basic "if" statements (EX. If IMyActiveAdmins == 0: setblock 30 30 30 redstone_block )