Wow, actually found it just after posting this thread after hours of searching.

They are:
sim/instruments/DG_sync_down
sim/instruments/DG_sync_up

In X-Plane they are:
vacuum DG sync down
vacuum DG sync up

Hi Jordi,

Make sure to restart XP11 after activating an aircraft, and reload the aircraft if you've changed the screen resolution or window size. You might also need to change the UI size to 100%.

Thanks
Martyn

Just to clarify, the lack of feedback is due to this not being a support forum so no guarantee of us reading every post.

Apart from submitting a support ticket, the best place to go for discussion of our XP11 aircraft is - https://forums.x-plane.org/index.php?/forums/forum/473-c152/

That forum is very active so the development team are usually lurking around and will answer questions where possible.

Our entire XP11 fleet received significant updates in early September to bring them up to the latest XP11.50 standards, including flight dynamics, as well as fixing a variety of bugs that had cropped up since the previous updates.

https://support.justflight.com/en/support/solutions/articles/17000085809-c152-xp-changelog

As Andy has posted, you can adjust the transparency of the menu arrow using your mouse-wheel.

We'll investigate the sounds and add any that are currently missing. There will be some differences in functionality and aircraft behaviour due to the differences in the two simulators.

@Mike-Cameron I have the same question, disappointed that this was never addressed. I took lessons in an old 150 and would like the old-school avionics.

Frankie, try this:
https://community.justflight.com/topic/533/figured-out-panel-selector-not-displaying-issue

@Voice-of-Reason Yup thank you!