The activation/deactivation of a user can be done by the account owner, or by a user with administrator rights. You cannot deactivate your own user.
To activate/deactivate employee user accounts, first navigate to your company profile.
Now open the 'Employees' (1) tab and then click on 'Expand all' (2).
A list of all employees appears (including deactivated user accounts).
You can now select the desired employee.
Depending on the current user account status (deactivated or not), an option/button labelled 'Disable user' or 'Enable user' will appear in the 'Rights' tab (see screenshot).
This allows you to activate or deactivate the user via the corresponding button.
In order to ensure data consistency, deletion of employees that have activities (such as orders, quotes, exports, etc.) is not possible.
Deactivating these employees is sufficient, meaning access to the platform is no longer possible for these employees, and furthermore a user licence in your contract package becomes available again, allowing you to invite more colleagues.