Are portlets accessible and configurable via REST-API?
No support for portlets in plone.restapi .
Old PR. Reading portlets worked fine.
@tiberiuichim: Are there any reasons why this was abandoned?
There wasn't enough interest in the Volto world for portlets.
It is really a pity that the REST-API becomes mainly a Volto-API and ignores and obfuscates lots of good Plone functionality.
I know what you mean, but plone.restapi right now is driven by use and contributions. Volto is still under heavy development, so it's somewhat natural that it drives plone.restapi.
Sure, feel free to continue work on that branch. Make sure to coordinate also with @tisto, the current plone.restapi maintainer
it could also be moved into an addon.