Material Collection Parameter is blank

So im trying to make an opacity map so I can make the walls between my character and my camera transparent however when I go to make a Material Collection Parameters it always ends up being blank and having to editable variables.

I’m going to bump this since I am experiencing the exact same issue and have not found ANY kind of answer anywhere. The only thing I can add to this is that it’s happening everywhere I can add arrays. For instance, it doesn’t work in Material Parameter Collection just as it doesn’t work in Landscape Grass Types. This is a really irritating bug with no apparent fix and it’s driving me insane. If the original poster of this issue found an answer then PLEASE post back what it was so no one else goes through the struggle.

I found the solution and I’m posting here to save all of you the trouble. I hope you find this longer than it took me.

Open up whatever is blank, be it the MPC or a Landscape Grass type, whatever. When you open it, click on the window tab, and make sure that DETAILS in the top has a check next to it

Once you check that, everything should come back up and you should be able to use as normal.