Motivation
This is a QoL feature that could be useful. If you try to delete a folder containing a model file that's loaded in chaiNNer, Windows will say you don't have permissions. If this is intentional, a quick way to clear the loaded model (rather than loading another model, deleting the node, or closing the program entirely) would come in handy.

Description
Implementation could be either an "x" button inside the Model field, next to the loaded model name, or right click > clear.

Alternatives
Another solution is to just allow the deletion of the files, then display a file not found error in chaiNNer.