Description of the feature

I had had the experience of adding a Creative Upgrade, and due to boredom I filled it to over 100k items. when I removed the upgrade, it dropped all the items to over the world and lagged the hell out of me. So my suggestion is to not allow a drawer upgrade to be removed until the items amount fall below a certain threshold

How does it make the mod better?

Can possibly hotfix a lag machine abuse

This does indeed seem like a problem. Do you happen to know how storage drawers handles this?

I don't understand the question. At code level I don't know how the drawer handle it. but Interactively, if you remove the upgrade, it will automatically empty the drawer slot from the excess onto the world until it reaches the storage capacity of the slot.

I asked if you know how the forge equivalent "Storage Drawers" handles this.

I didn't even know there was a Forge equivalent. So nope. I don't know.
Edit: I'll edit this again once I find out and you haven't answered
Edit2: Not sure how exactly the drawers work, but it seems you can't remove the upgrade. Not sure tbh, I didn't install REI, so I couldn't see what were all the items that the mod added

Anyways, I'll add this with a config toggle

Storage drawers prevents you from removing upgrades which would cause it to drop items.

This has been fixed in version 1.3.2. Feel free to reopen if the issue persists.