The visual bug is fixed. In my testing I did have a confusing moment when an item refused to discard but I realized you can only discard items in its original zone (i.e. a sword from the red zone moved to the player inventory won't be discardable until moved back to the red zone, and vice versa). Not a huge deal but I can see it leading the player to a confusing moment like it did for me.
I added a series of parameters so that the system doesn't distinguish between an item in the extra grid and an item in the normal inventory grid, so all options will be available for both types of items. Please download the v3.9 file again; I believe everything is now in order. Thank you for all the feedback; I am truly grateful for your help in improving this tool.