Deactivate a user, by following these steps: 


  1. In the top menu bar click on the profile image.
  2. Select settings from the options. 
  3. Select Organization from the settings menu
  4. Select Users tab
  5. Click the options icon beside the user to be deactivated and select deactivate
  6. The deactivated user now won't be able to login to your Slenke workspace, their posts, tasks, and messages are kept and are accessible after the deactivation.