Cisco Trunking and NetGear

I've just inhereted a mess of a network of differeing NetGear hardware all setup as a flat VLAN with all IT and OT in the same ip schema. While I'm a Cisco deciple, I want to re-purpose the existing switches at the access edge but am struggling with understanding how to do it with the GUI vs as I would with the CLI in a Cicso envrionment.

i have installed some Cisco 9300's as L2 in a stack as my core, trunking to a SonicWall for routing, which works fine.

Now, I'm trying to trunk my GS752 to the Cisco 9300's but keep having to factory-reset the GS752's as I get locked out.

I have designated ports on the Cisco side as trunks, and in that envrionment created my VLANs. Now, I'm trying to 

1) Specify the Management VLAN so that I can secure the Control Plane for all the switches as different from the Data Plane

2) I understand that the GS switches don't support VTP so you have to implicitly define all the VLANs you want to appear on the downstream switch within the GUI. I also found the Global Auto-Trunk Mode option but assume that it doesn't function the same as when you do this on a Cisco switch so i can't use it. I have defined the VLANs I want to appear on the switch in the VLAN Configuration page but how can I both define the VLANs, set the Management VLAN and set the uplink port as Tagged (switchport mode trunk) in the same session? I always get disconnected and have to factory reset. Having a dedicated management port would be so much easier.

Is there a special order to do this? Do I 1st define the VLAN (in this case 7) in VLAN Configuration then Tag the uplink port with VLAN 7 in VLAN Membership then set the Management VLAN (as 7) in IP Configuration?

It seems that as soon as I tag the port, i lose access.

thanks