Managing Fortiswitch from Fortimanager

I'm a bit at a loss here. We just bought 2 fortiswitch 148E (one poe and the other not) to replace our aging no-name switch at our office. We have a pair of 81E in A-P HA. I was able to add the switchs to the gate after seting a dedicated fortilink port (port 10). At the moment, I have another port (port 2) that is used to uplink to the switch stack, and the office vlans are attached to that.

Ideally, I will want to move those vlan to the fortilink port and since we connot change the physicial interface attached to a vlan, and it would verry complicated to completly remove the vlans, dhcp server etc, and the re-create it on that second port ?

Next, in fmg, as I understand it I need to attach a template to a switch so that ports are assigne to the righ vlan, so I created an empty one, where all ports are assigned to "default.vswport" and allowed vlans to "default.qtnport". When I try to install the config, I get : "vdom copy error: entry not exist. detail: Default port qtn.port10 does not exist on device". What did I miss ?