I have many wants for improvements, but considering QoL are usually less impactful things, I'd say...

On Glamours: Checkboxes to let you use just specific equipment slots of a glamour plate - for example, I'm out there and I just want to change to a head piece from the glamour plate 3. Today to do this, I need to un-equip all of my gear but the slot I want - glamour it and then re-equip everything. Doable, but not handy at all.

On Battle Gauges: Let you have the toggle option to track more things there, especially debuffs like dots on your main target, or timed buffs. The usual way of tracking those is really bad for me. Even separating the buffs into different categories, it still gets mixed up with some stuff that doesn't need immediate tracking and also hard to see in practical (not huge) sizes.

On vendors: Honestly, just do a big usability quality pass. There are so many QoL features that, even despite the few ones we got, still need much improvement. A tip, would be to organize more things in tabs, instead of different menus (e.g. the rain/agumentation vendor).

On Waymarks: Let us change (on our end) the waymarks to a cleaner version. Most of the time I personally just need to see the floating number or the waymark's box, not the flashy glowing effects.

On the Party Frame: Let us opt out of unecessary clutter information, like the header - I think I know that a Full Party is 8 people lol - or the numbers before people's names. Possibly a more compact way. I do much better with a minimalistic interface, and having that as an option would please everyone.

On chat interface: Chat bubbles. No, not just a QoL for roleplaying, but it's extremely handy to catch rez announcements or some sort of call in the middle of combat without having to look away to the chat box. Just make it a toggle so people bothered by them can choose.