Create a new group by first clicking on Groups in the left menu and then clicking on New group. Give the group a name, enter a description if you want, and add which users should belong to the group.
You can create multiple groups and a user can belong to several different groups. With the help of groups, you can easily put several users as responsible for checks and deviations, instead of having to assign an individual user, you can assign the entire group. All users in the group will then get the check/deviation in the My errands list. If a user resolves a deviation, it will disappear from the My errands list for the other group members as well.
You can also tag a group directly in a comment field instead of tagging an individual user. Then all members of the group will receive a push notification.