OBTW, here is what the "not working 100% modal looks like" ....
The reason it does not work perfectly, is that the editor page does not immediately update when a new attachment is added via the modal. This will require more reactive code (like VueJS) or maybe some additional jQuery; but since it works perfectly fine as "not a modal" right now, I'm going to let it stay as it for the time being until I get better at modal development.