It is possible to over fill the system to reduce lever throw - assuming the air comes out first - but it’s unlikely to stay consistent as the system adjusts to pad wear.
“Ninja level bleed trick over fill” needs to be done from the calliper and requires a special bleed block.
Well, if it’s shimano is pretty straight forward to add more mineral oil to the top chamber.
If the bike has been out riding I doubt there are any bubbles left in the hose, so it’s just a matter of topping up with mineral oil.