Probably no need to uninstall.
You might try going to User/App Data/Local/SketchUp/SketchUp 2019/SketchUp and editing the file called PrivatePreferences.json. Can you see ModalEditMaterialDlg?
The User/Appdata directory is normally hidden so you need to make it visible. Just searching for it in the Windows Explorer panel under your username should make it show.