@metaedit.bsky.social has been very useful for prototyping the language and its concrete syntax. The REPL aspect of the tool is really valuable for designing a metamodel and its concrete syntax based on examples, which co-evolve in a consistent manner.

It depends on the group as some are active still, but IMHO they are not so effective as earlier - earlier it was even possible to check quickly which your groups had recent discussion.

I see it a good trend as it aims to use modeling more extensively: not only for getting better understanding or communication, but also producing the actual code.

No reason to stop here. If interested to read about 100+ public cases on domain-specific modeling languages, see www.dsmforum.org/cases.html

Yes, there is something in the notation that indicates been represented in Diagram Editor of MetaEdit+. Are there some publications on these to read?

I wonder what is the domain these two metamodels aim towards... ;-)