could you add compatibility with this mod: https://www.curseforge.com/minecraft/mc-mods/city-modernities ?

I mean, they add paper money and you add coins, both can be stacked, and both are very well textured. I think they would work well together!

I do eventually plan on adding the ability for server owners to customize & register additional coins, however that will be a fairly complicated task that will require a complete overhaul of the coin system so do expect it to happen any time soon.

New coin chains can now be registered using the new MasterCoinList.json config added in v1.0.5.0. This should be more than enough to be able to make these two mods compatible.