Talk to HASBRO and Wotc about the Platform they hold the Copyright.
They hold the copyright for the IP.
Larian holds the copyright for BG3 itself.
Also, Larian owns the propriatary game engine used to create BG3.
What this means, is that HASBRO/WotC have control over the DnD IP, they can use all characters from BG3 as well as reuse the Baldur's Gate name.
But they cannot have anyone work on BG3 without Larian's permission. In addition, anyone who works on BG3 would need access to the Divinity Engine that Larian is in sole control of (And are unlikely to relinquish control over given that it's the platform for their other games too)
As such, if HASBRO/WotC wanted to make some sort of "RPG Maker" platform (Which might still be copyrighted to the actual "RPG Maker" tool that exists already for making old school pixel based RPG's) they'd want to create it using a publicly available engine, such as Unreal 5 or Unity. That way they don't have to get permission from Larian to allow people to use it. It would also need to be made in a way that specifically enables people to utilize it to create campaigns with things like a toolkit (Like the ones that Bethesda games have to enable easier modding of their titles) otherwise actually adding stuff like a campaign would take a full dedicated team of developers several years worth of work.
Of course, this would mean a lot of rule changes because of how Larian tweaked rules for their engine (Such as the use of surfaces).
Also, it would mean people buy the tool once and then play infinite games for free that players make for free. Which is very much the opposite of how HASBRO/WotC operates... They'd be more likely to make you have to pay to access other people's campaigns...
