This is one of those questions that is both very easy to answer, but also has some devil in the details.
One thing you need to understand that Cisco is very port-centric in terms of config, and Extreme is very VLAN-centric. This leads sometimes to some confusion as you go from one to the other. I use both and I slightly prefer the VLAN approach when doing other things (eg: L3 routing) as the VLAN makes a bit more sense as the logical entity to which other things (eg: ports, IP addresses, etc.) are attached.
With an Extreme switch, you create VLANs and then add ports to them, rather than specifying what VLAN(s) should be permitted on a port.
If you add a VLAN untagged to the port, you're making it an access port (or setting the native VLAN if there are multiple other tagged VLANs on the port). If you add one or more VLANs tagged to a port, then it is effectively a trunk port.
There's no direct concept of just setting a port mode to trunk port and telling it to carry all VLANs. On an Extreme switch, VLANs must be created and added to the ports in question - this can seem a real pain in the backside but you eventually end up liking it as it stops all manner of problems with loops. For this reason, STP is disabled by default on an Extreme switch as it isn't really needed.
So if I have three VLANs, 'work', 'guest' and 'wifi' I can do something like this on two switches:
create vlan work tag 10
create vlan guest tag 11
create vlan wifi tag 12
config vlan work add port 1 untagged
config vlan guest add port 2 untagged
config vlan wifi add port 3 untagged
config vlan work add port 24 tagged
config vlan guest add port 24 tagged
config vlan wifi add port 24 tagged
This will make port 24 a trunk port between the switches, and the VLANs mentioned will be on ports 1 2 and 3 (as access / native ports).
If I created a new vlan:
create vlan somethingelse tag 20
and then added it like this
config vlan somethingelse add port 4 untagged
on both switches, it wouldn't appear automatically on the trunk. You'd need to explicitly add it:
config vlan somethingelse add port 24 tagged
You could also add it untagged on the port:
config vlan somethingelse del port 24
config vlan somethingelse add port 24 untagged
That would make VLAN 'somethingelse' the native VLAN on the trunk, with VLANs 'work', 'guest' and 'wifi' the trunked (tagged) vlans.
You don't need to add 'untagged' to the end of the add port command, it is the default - but I've put it in here for clarity.
Paul.