Add System to Existing DAT

Upload the site's existing .dat on the left and a .dsbx containing the new system on the right. Existing groups are locked in their slots; the new groups fill the free slots and can be dragged anywhere that's open, sorted A→Z, or renamed with a double-click. The controller name, IP and every other setting in the .dat stay unchanged. If a new unit uses an M-Net address that's already on the controller, the download stays off until you fix the address in DSB and re-upload the .dsbx.