Maybe I can find an answer here. If not, well, feedback.

It doesn't seem like you can save portraits in a way that permanently saves your outfit used to create that specific portrait... If you link it to your Adventurer Plate, it'll stay as is, but if not, I notice all other saved portraits will always change to reflect your current glamour/job weapon.

I was hoping I could make multiple portraits for different jobs and glamours, with specific poses/outfits to link to gearsets- but in the end they're perpetually linked to what you're currently wearing if it's not the active portrait being used for your Adventurer Plate.