There are too many variables in play here to answer a solid yes or no.
On the street, you should never push to the point where you have no room for error or escape. So in that situation, if you are riding safely on the street, then yes, you may/can add lean angle at any point through the corner.
However, once the pace picks up, the margin or error goes out the window, and you start really pushing the bike (on the track), the amount of changes you can make mid-corner get less and less. Any change, be it lean angle, speed, BP, hand/arm/leg/foot position, and you can lowside with the quickness. The idea is to be able to make small changes as smooth as possible. For example, if I am in a long corner, and need to scrub off speed (like T1 at Roebling), I will allow the bike to run wide, keeping the same lean angle, which in turn will slow me down a bit. I will also feed in a little rear brake if I need to tighten up my line mid-corner, but that is something I don't recommend anyone trying unless you are very experienced since it can lead to very bad outcomes.