How it works:
There's start active which means as soon as you join your get it but you don't want to copy paste a ton of them right now so you make it "for all" meaning anyone who joins while get their own and what if you want to get it themselves then you add the options for triggers to make items follow you this can be used for inventory, horror, pets and etc.
(I wrote this before the top part so ignore me explaining new ideas)
For example basically you could go to selection for a block then make it so it's "for all" which it will give anyone who joins a map whenever they join the items that you have made and "start active" or when you step into a trigger for example, an inventory, I would make 5 transparent blocks with triggers on them and have them on start active and "for all" and set them as a following block, then make my items that I want people to hold like a block and sword and when they drop the items in any of the transparent blocks it activates the trigger and groups them so they stay in the blocks and follow you as well. You could also have a pet, you can make it so when you pay their head or touch them they then follow you around and it gives you a "remote" to make them sit, bark or jump, and think of the possibilities for horror games
I think this could be a very awesome sauce feature.