Hello,
yes you can set a a variable in another blueprint. First you create a variable and select the blueprint you want to use as type. (or use a “actor from class” with the bp selected or any other way to have your parent actor)
Then you drag a “cast” from it.
From this one you drag the variable you want set.
But this is for usual blueprints which are in a level blueprint. Level blueprints are not common blueprints. It needs to send your datas from a level to another one.