Whilst blueprints don’t have straight “pick random” node, you can make your own i guess as it has random integer within range node.
So if you have, lets say 3 effects you generate random int within 0-2 range (with options being 0, 1, 2) and then compare it to 0, 1, 2.
If generated int equals 0 then spawn effect #1, if generated int equals 1 then spawn effect #2 and if the int equals 2 then spawn effect #3.
Perhaps there’s an easier/faster way of doing this, but this is what i can think of now.