Very cool! @korelstar@github.com submitted a patch to #Nextcloud Notes for setting a default file extension/suffix: https://github.com/nextcloud/notes/pull/223
The current behavior is to create a .txt file, despite the editor supporting markdown as a use-case. It kinda sucks, because it will rename my files from .md to .txt, unless I name the title of the document the filename (first line should be 'filename.md'). This is a welcome addition!