Hey there, I made (more like copied) a thing again: https://nicofrand.eu/roundav-a-roundcube-plugin-to-save-to-attach-files-from-your-webdav-ex-nextcloud/

That's a plugin that links your #roundcubemail to your #nextcloud, allowing you to save attachments to your cloud, or attach files from it.

The code is messy, the Roundcube's plugin API not so great, but it works for me.

One more project to maintain. That's one too much, so if you encounter a bug and are able to fix it, pull requests are welcome!