You can only assign one location/department to each employee, not multiple.
As a rule, when people ask for multiple locations/departments, they don’t actually want to assign multiple locations/departments to one employee; they have a different goal. Depending on the goal, you can achieve it as follows:
1) When filtering by location/department, an employee should appear for more than one selection
You can solve this by creating user groups. Sign in to Timebutler and click “Settings > User groups” at the bottom left, then create a new user group, for example named “Location Munich”, and add the users (Note: if you select the “Shared user group” option, other users will also have access to this group). Now create another user group, for example “Location Dortmund”, and add the employees.
With groups, you can add an employee to multiple groups. So you can add an employee to both “Location Munich” and “Location Dortmund”.
As soon as you have created the groups, Timebutler automatically shows an option to filter by user group in most views in the filter (green “Show filter” button at the top right).
2) Users should get visibility permissions for employees who should be assigned to two/multiple departments/locations
For this case, first create the user groups, as described in the answer above in 1). Then sign in to Timebutler as an admin and click “Settings > Visibility permissions” at the bottom left. You can now grant visibility permissions for the user groups.
3) Multiple supervisors should approve the requests of one or more employees
You don’t need to assign multiple departments/locations to an employee for this.
You can assign one or more supervisors to each user. Read here [how to set up multiple supervisors for employees(/frequently-asked-questions/user-accounts/assign-multiple-supervisors/).