Cloning and tweaking instead of having to start from scratch is much easier for people.
This may be a step towards solving some of the UX issues discussed in #1519 too. Site admins seem to be using the "Full HTML" format as a go-to solution when content editors demand more. This is OK in general, but it creates false expectations that people will get a WYSIWYG etc.
If we provided an easy way for admins to clone the "Filtered HTML" format, then they would do that, and add buttons + allow additional HTML tags as required (which is what they should be doing).
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@willowf If you have the time and patience for OG I don't think you'll regret it.
Create groups or communities with nodes or Organic groups
And another note: OG has a bit of a learning curve. It's not very intuitive, but I believe there is good ducomentation in its wiki page. https://github.com/backdrop-contrib/og/wiki
Create groups or communities with nodes or Organic groups
Organic Group is a very comprehensive (and somewhat heavy) solution (disclosure: I'm a maintainer). If what you need is fairly simple (from your description that seems to be the case), what you...
Create groups or communities with nodes or Organic groups