Assuming the user has already worked in the application, it will not be possible to delete them (however, you can set their access to Read Only — so that no license is consumed — and assign them the BLOCKED role, which restricts access to all records).
If you do not wish to use the license for another user and would like to cancel it, please contact our sales department (obchodflexi@abra.eu; podporaflexi@abra.eu).