D&D Miniature Markers and Converters

As a 5e D&D DM, I typically use collectable miniatures first and then supplement them with 3D printed versions when they are either too expensive, or have not been produced yet. Also, since I've started collecting fairly recently (mostly Icons of the Realms sets), I've ended up with a lot of duplicates that can be hard to track individually when they all get put on the map at the same time.

I'm constantly looking for ways to speed up the game mechanics when handling large groups of creatures