Hey, I'm having trouble using the blacklist config Banned Mobs in the spawner.cfg.
I've tried with the following values:

quark:stoneling
stoneling
"quark:stoneling"
"stoneling"

At this point I'm a bit sick of /reloading, could you tell me what the correct syntax is please? :)

quark:stoneling should be the proper syntax assuming thats the registry name.
Also those configs don't support /reload, unfortunately.

That did the trick, thanks - I thought /reload worked so I hadn't actually tried quark:stoneling
Sidenote, I was given the advancement Spawner Modifier when I clicked a spawner with the blacklisted spawn egg for quark:stoneling, I was not given that advancement when it was not blacklisted.