https://docs.moodle.org/33/en/RTCollaboration
"Warning: This plugin has not been maintained since Moodle 2.1 and is unlikely to work with current, supported versions of Moodle."
https://www.google.com/search?q=moodle+plugins+collaboration&ie=utf-8&oe=utf-8
How about Google Drive/Docs? or other online office suite that offers collaboration?
Those could be assignments in Moodle, but would require, in some cases, students to have google accounts. No expense to students, however, as those accounts are free.
https://www.google.com/search?q=google+docs+collaboration+features&ie=utf-8&oe=utf-8
'spirit of sharing', Ken