@Joseph-TP 

The problem is not that I can’t remove offline devices from the VPN section. The issue is that when I try to add new devices, the old offline devices are still there. I don’t understand why they remain if I have already deleted them—like when I replace my old phone and remove it so it’s no longer listed. However, when I try to add my new phone in the VPN section, the old one still appears, even though I deleted it from the offline devices list. Either the VPN section should sync these devices properly, or there should be an option to remove unused devices directly from there.

  @Joseph-TP 

Yes, on all my devices, the deleted offline devices still appear in the web interface when I try to add a new device in the VPN client section. However, the offline devices do sync with the Tether app—if I delete an offline device in the Tether app, it also gets removed from the web interface's client list. But when adding a new device in the VPN section, all previously deleted offline devices are still listed there.