Concurrent editing or Collaborative real-time (https://en.wikipedia.org/wiki/Collaborative_real-time_editor) is perhaps a better choice words.

Notion is supposedly able to do it: https://www.notion.so/help/collaborate-within-a-workspace#re....

Wikimedia is apparently working on it: https://www.mediawiki.org/wiki/VisualEditor/Real-time_collab...