GM. Tweaked neck is making a slow recovery.

What exercises (if any) have been transformative for your own posture and desk-work endurance?

There could be very seemingly unrelated problems that are the cause, if you only deal with the effect instead it will take time to fix, so do 'spine hygiene' routines, one thing I'd make sure to attend is the curvature of the lower back, particularly if you are sitting for to many hours or sleeping flat face upwards.

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Tell me more, how do you attend to that? What are the symptoms?

Try so correct your spine curvature, you could lay in bed with a pillow on your lower back (and no pillow on the head), just for 20 min, a couple of times a day if possible, if it makes a difference with your neck then you know is about posture, it could also be other things but try this first.