Which roswtf plugins can be installed and how?

edit

I can't say for certain, but I doubt there are any plugins for roswtf other than the one in tf.

Six reasons for that:

1. the wiki/roswtf page shows only two Used by entries: that list is based on the info in the package manifest, and plugins typically have a run_depend and / or build_depend on the package that they are providing plugins for. In this case that list only contains tf and ros_comm. ros_comm is roswtf's metapackage, so doesn't count. That leaves tf, which does indeed have an export line for a roswtf plugin.
2. the wiki/roswtf/Plugins page states that the plugin API is "very experimental", which doesn't invite people to contribute / write plugins.
3. a Google search (this one) for "roswtf plugin" package.xml does not return any real results for me other than wiki mirrors, the above mentioned API wiki page, package manifest specs and similar pages. And of course the package.xml of tf.
4. A Github search (this one) doesn't return anything other than the package.xml of various cloned/forked/copied tf packages.
5. rospack plugins --attrib=plugin roswtf returns only tf on a system with 'all' ROS packages installed (apt install ros-$distro-*).
6. I've never seen any other than the tf one (weak, I know).

Note that 1 is actually not 'exhaustive', as the used by list can only show pkgs the ROS buildfarm knows about. It could well be that users/companies/organisations have written roswtf plugins that were never/aren't released.

But I would've expected the Google search to show some results in that case.