How to save PowerPoint pen annotations without leaving the Slideshow mode

Question

I write alot of annotaions using the pen on my PowerPoint slide while presenting on a projector. For the first few annotaions, writing comes out smooth without a delay, but with more and more annotations, the ink starts to come out after a substantial delay which is very annoying.

I noticed that if I stop mid-way and save my file with the Keep annotations option, PowerPoint becomes snappy again. This is also annoying as I have to leave the Slideshow mode and the audience would loose track of what I'm saying. I tried every possible keyboard shortcut I know of to save my wrok while presenting without success, ctrl+s, SHIFT+F12, F12, ALT+F2, etc., nothing works. I appreciate your help.