+1 on this in general.

In Detail I'd also like to use something like this to model distant-future "to-be" landscapes, where I start out with a duplicate (now, as there's no referencing yet) of the current one and for the most part add new objects, re-model the diagrams.

Would be nice to keep the existing objects in sync from the current landscape (editing only supported there). Would also be nice to eventually share back some "newly created" objects from the "to-be" landscape to the current-existing one.

I know there's the Draft-Feature partially adressing this, but my usecase is more long-term and spans whole landscapes, not only a single diagram.

This is critical (imo) to allow a more sustainable separation of larger complex landscapes. It is not as simple as having ownership of objects restricted. I want to be able to have a specific part of the larger landscape separated and then owned/maintained by a specific department/market. But also keeping the ability to reference systems/apps between landscapes is still needed to ensure no needless duplication