adjusting points of a polygon

I created a mask with a polygon node and now I want to adjust it on different frames but when I use keys like s,t,x,y, etc. it isn't even working with the trackpad. so, I used a pen tablet. it was working with the tablet but I can't apply the changes made. whenever I click somewhere else to apply it just reset the center point of transformation. what is the problem here? am I missing something?