Found something out on Windows that is called 'DirectShow'. Although, did not know how it works since I'm a baby programmer but did found out that on application that it is being used (VIDStudio, Elektronika).
It allows to capture the out output to VLC that can be recorded. Hope to have such feature in OpenLP which will allows to record the projection.
On Alert, please can the width of be specified so that it do not fill the whole width of the screen and also ability to choose transparent background.
God bless you.