Currently in the configs to add a mob to the list of mobs that would drop coins, we have to do it one by one, I suggest adding the capability of adding a wildcard to the config to allow all mobs in a namespace to drop coins.

This is wrong, as you are able to use tags. This gives you greater control and is usually supported by mods which add relevant types of mobs. An example is the #minecraft:undead tag, which includes #minecraft:zombies and minecraft:skeletons, plus phantoms and withers.
For vanilla tags I suggest looking at the Minecraft Wiki.

Ah pardon my ignorance on that issue, but what about mobs that are not under any of those tags?

This can depend on mod to mod. Some provide tag support using vanilla tags (for important functionality, like whether the Smite enchantment applies). Others do not.
I believe there are some REI, EMI or JEI plugins which let you see entity tags with their contents. Otherwise, vanilla lists the tags themselves when running commands like /kill @e[type=#<tagname>]
As for modifying them, you can easily add new or modify entries to tags using datapacks or modpack tools (I E. KubeJS).

Got it, thanks for explaining the tagging system I’ll work with that for now. I still think built-in wildcard support could be handy for a quicker setup, so maybe it could be something to revisit in the future. Either way, thanks for the pointers!