They wrote in
https://baldursgate3.game/news/community-update-27-official-modding-support_118We are currently seeing how far we can offer guidance for unsupported mods, which - at present - includes discussing whether we create official scripting API documentation, and whether we introduce internal testing for the Script Extender and other tools to support compatibility between patches where possible. However, while we can guide, we cannot offer support for mods outside of our pipeline.
and
Load levels read-only to look at all the local entities, as well as the setup, and test your mods in-game while creating them.
So there most likely won’t be an official toolkit to create campaigns, because
Baldur’s Gate 3, as a Dungeons & Dragons game licensed by our partners, has certain guidelines in place to ensure the integrity of the game’s universe.
but
While some NSFW mods and certain script-heavy modifications may not be supported through the official pipeline, modding outside of our pipeline will still be an option.
That sounds like inofficial tools may be able to do these changes and the result could be validated with the official tools (“load levels read-only”). And they may actually validate that their updates do not break unofficial modding tools (within limits).
So I have my hopes up, but they do not (and cannot) make promises.
