Add a button that allows you to favorite certain materials in the material gun which puts it at the top of the list. Another cool addition would be to filter rocks, trees and ores. Also having named folders would be a good addition.
For easy use the folders could be a drag and drop system. And for the create folder, favourite and filter buttons would be listed at the top.
Filter would be a drop down listing rocks, ore, wood, refined, planked etc..
Favourite would be the same as the delete material, but instead when clicking on the material it puts it at the top.
Folders would just be a customisable colour and name that gets put at the top of the mat gun.