If you want to remove a user from a specific group, please follow these steps: |1| Go to pAdmin > Groups & Users > Edit groups |2| You will see the following form: 
|3| You will notice, that there are some different kind of groups: Shared groups, Included groups, ordinary groups, master groups and Subgroups .
 Warning: a user us in a master group only then, when he is a member of at least one of its subgroups.
Click on the icon next to the group name
|4| You will see the following form:

In order to remove the user from the group, just click on the icon in the collumn "remove".
 Note: If you want to remove the user from the whole platform, you have to perform these steps for the main group of the platform
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