Thanks for the answers from both of you.

Admittedly, haven’t sought a doctor/physio yet mostly because it’s always felt like something that’s incredibly minor, but just doesn’t seem to be going away, so unfortunately seems the direction I’m going to have to take at some point.

No pain at the back of the knee at all. It’s all front-area, so I hadn't considered bakers cyst

No locking, no giving way, no (as far as I can tell) reduced flexibility/mobility. When stood leg fully locked, there is a tightness in the knee area, but at the same time this with a resistance band stretching out the leg has always felt good.
I had considered meniscal but thought I’d be in a lot more pain.

Initially I tried a few half-squats recommended for meniscal/pes anserine but these irritated the shooting pain on the right-hand side of the knee (not the left where the initial walking pain was), pain feedback was after doing a few days of doing it, and then it seemed to hurt every time I attempted it so backed off – did nothing, and it went back to the status quo of not mild sensation when walking and persistent ache when resting which is helped by movement/walking.

For example, this morning ache came on, went for half an hour walk, whilst felt odd sensation, no pain present, and the ache disappears, and doesn’t return until at rest.

The typical floor quad stretch is extremely tight/uncomfortable in the knee and irritates the aching sensation afterwards/next day etc so I’ve avoided that, at the moment I’m in an ache flare up because of what I suspect is from quad stretches.

Knee has always been a bit of a cracker/clicker, felt more clicks than normal initially but at the moment seems to be like it was before in terms of clicking/cracking, never with any pain.

At the moment I’m focusing on cross band lateral walks/glutes and do a lot of quad foam rolling.