Hi everyone,
I searched a lot and was surprised nobody has addressed the issue of extending and retracting the actuators in Lego Digital Designer OR I was unable to find it - be it through searching here, google, youtube or any other means.
So I discovered a little trick to do this. If it already exists here in these forums, then I'm really sorry and please accept my apologies.
The trick involves exporting the file to *.lxfml and editing the coordinates of sub-components of actuators manually with text editor and is easily doable by anyone without the need for expertise or special tools etc. Below is my video of this: