How do I set the scale of an actor to grow/shrink according to how many items are in my inventory?

You can get the length of your array and set it as the scale or you can store a float value in your struct as the size increase value that you add to your current scale.

I noticed that the default value for Item Vector is 0,0,0 and I’m not sure how you’re setting it but that’s probably why the scale doesn’t schange.