Drag and drop files in Tkinter GUI
Unfortunately, tkinter only supports experimental widget drag and drop, nothing else. I ran into similar problems trying to make a complex GUI.
I would look into wxPython. It's complex, Object Oriented, and daunting, but has and unbelievable amount of features that reward you for learning it. Including file drag and drop.
Look at the wxPython thumbnails at https://wxpython.org/Phoenix/docs/html/gallery.html for images of what the widgets look like. The thumbnails include images for about half of the available widgets. The images are also a bit out of date.
Look at pronounced https://pythonlibrary.org or https://zetcode.com for the best tutorials. After them, your best resource is Google and the forums.