This is a Backend-related extension to manage both Backend and Frontend users from the edit form of Backend/Frontend groups. Easily assign users to groups or remove them from groups.
Clone this repository into typo3conf/ext/mr_usrgrpmgmt:
$ cd /path/to/typo3conf/ext/ $ git clone https://github.com/xperseguers/t3ext-mr_usrgrpmgmt.git mr_usrgrpmgmt
Proceed as usual
Read more in the manual.