Just tried out the new stuff, and it's a great addition! I really like the percentage mode implementation, it just needs that % symbol. I also like how it can go above 100%, which might have a good use, say for train stations and keeping count of stock. Right now I've set up a display to show my current stations capacity using a 3 digit percentage display and a 5 digit unit display to show me the total amount of stock.
Some more ideas:
A display that can visually show the percentage as a meter/bar, with colorization going from red to green.
A button to enable the display to show on map view with the item icon + number (not sure if possible)
Add support for copying and pasting display settings to another display like with other machines.
Adding an option to manually enter a string format for the display.