i just did some testing, and there is actually indeed a geo limit! hk wiki listed it as 9,999,999, so i edited my save file to that value and then collected some geo (specifically crystal guardian geo) and while the number did briefly appear to go above 9,999,999, it then capped back down to the limit. dragging the save file back into the save editor showed me that it was still at the limit, which means the visual and the hard limit is the same. which means that max geo would indeed be possible, and as i have been told, has been done before
however, running it nmg would be both boring and slow, so i don't really think anyone would want to run it. running it with all glitches is much more doable. i still don't know who would want to run it though.
if you want a geo grind category you could do All Unbreakable Charms. It's not on src but a few people have done it
all unbreakables ag is a really funny category because of the blind oob movement that exists in literally no other category, and you really only are there because it's the fastest place to get an absurd amount of geo. max geo would be standing in the infinite geo pit and shrieking for 15 minutes instead of save quitting and buying the charms after you've done it an acceptable number of times. i have tried doing the former and getting to max geo was funny the one time but also boring. don't recommend it. just run all unbreakbles tbh
