Thanks for playing! And thank you for the suggestions. Adding the ability to right click + drag to remove multiple tiles is a good idea and I can probably add that.
With respect to your mod suggestions, I'll have to do some investigation. I'm not sure how well my infrastructure would support those behaviors and I'd also need to make sure it is still intuitive to new players.
While it is not an elegant solution, if you want to experiment with your grid without messing it up, you can leverage how the autosave works. The game is only saved immediately after you pick a reward and when you press the Start button. This means you can mess around with your grid, quit to the main menu, then hit continue to restore the grid state.