Refresh the UV Map with a new topology I will use an easy example to focus my problem. 

I have a cylinder, with this unwrap below. I scaled and moved the islands in the UV layout in order to optimize my UVs. 

Right now, I don't want to modify my Uvs' island more . . . Suppose island's position and scale are perfect for my purposes. They have just to stay there. 



Here's the problem: I can't export my cylinder with this topology (problem of my engine) then I have to fix my mesh in this way:



I didn't touch any mark seams during the process.

My question is: is there a command or a path in order to refresh the UV map? I would like to "refresh" the UV map with the new topology for the top and bottom face of cylinder without doing again the unwrap and scale-move my island.

P.S. I don't want to move again my UVs' islands because I already created the texture (with the first UV) and I'm afraid of not bieng able to match all perfectly with a new unwrap.

Thank you!
In this example you have 2 options. One is to poke face, which will divide it without distorting UV map and second is to pin vertices of the UV map, do what you need to do with the face and unwrap everything again without moving UV map.
Here is how it's done: