A way to make mobs from a trial spawner glow

I have a small idea about trial spawners that can be nice for a lot of people: sometimes, you can be in a fight with the mobs from a trial spawner, but it seems like some mobs are hiding in dumb places, its even more ridiculous with cave spiders that sticks to the corner of walls where you can't see them. So here is my suggestion: with a right click on the trial spawner with an empty hand, or, if its too powerful, an item like glow berries or glow ink sack, every remaining mob from the trial spawner will start glowing so you can find them more easily!