I notice it when doing side planks. I can do them on my right side (though, admittedly not for long), but on the left I have to modify - can't even lift myself into a left plank, let alone stay there, so am forced to do the left side modified, which is really only going to increase the strength discrepancy if I'm only modifying the plank on the left.
I imagine the imbalance is most likely because I've always carried my handbag on the right side. Since I have a habit of toting books around with me, it's probably a little heavier than the average ladies' handbag.
It's not a visual concern. I still have too much belly fat to even notice if one oblique is bigger than the other, honestly, but the strength between the two sides is significantly different.
Any tips for balancing out? I keep trying to remind myself to carry the handbag on the left, but it's so automatic to pick it up on the right that by the time I remember, I'm usually already putting it down. :)
Firstly, I'd say stop carrying your bag on one shoulder all the time. It's terrible for your back in the long term. Either consciously alternate which shoulder you carry it on, or ideally throw it away and buy a good ruck sack.
I honestly don't see much benefit in trying to compensate for a poorly-carried heavy shoulder-bag through exercise. Much better to sort the actual source of the problem out! I hope I've been helpful