I've never used the Store version, but what you're looking to do should be possible.
First off download the latest Portable version of MB (not the Installer) and place it in a directory outside of Windows control. I suggest something like C:\MusicBee. This will work even while the Store version is installed. The major plus of using the Portable version is that if while trying to configure it like your previous version, you can easily delete it and start over. Also, backing up is as simple as copying C:\MusicBee to a flash drive or some other device and restoring from there.
- In menu bar of your Store version > Edit > Saved Settings > Save Settings Snapsho.
- In the menu bar of your Store version > Import/Export > Export Panel Arrangement.
- Open the Portable version and restore (load) the saved settings, followed by importing the panel arrangement.
- Once you're satisfied that the Portable version is to your liking, you can uninstall the Store version. And live happily ever after.