Why Not Make Prefabs

It's a bad solution

When you create a prefab by dragging a Grid with child Tilemaps to the Project folder, all references to Objects in the Scene are lost just like any other Prefab that you might create. This includes all TPT tiles. If you were to open the Prefab, the locations where TPT tiles had been placed would be replaced with pink or other oddly colored tiles.

TilePlus Won't Let You

If you mouse-drag a Tilemap or any GameObject that has Tilemaps as child GameObjects into a project folder to create a prefab, and there are any TPT tiles, the system will warn you in the console and will unlink the items you dragged from when you created this prefab so that the scene Tilemaps won’t be corrupted. You may as well delete the prefab that you created as it isn’t useful.