I am trying to figure out how to add multiple network interfaces to a vm. Not pass through or physical interfaces. Just virtual ones.

I didn't see a way to do it in the web page while creating or afterward.

I've searched various ways and can't seem to find an answer for this.

you need to edit the xml file directly

switch to xml view of the vm, locate the part that belongs to the main lan. copy & paste it and modify the names/values.

After saving the xml and starting the vm the additional lan card(s) will show up in the gui too.

(The same is true for other devices like disks and so on)

Be aware that a syntax error in the xml will keep the vm from starting! So be careful with your edits. Save the orginal beforehand!