Is there any automatic (or manual but easy) way to correct keystoning? (Where buildings look to be leaning backwards?)

I shoot architecture so having vertical lines be straigh up and down is really hard to do with a gimbal and a wide angle lens.

I have tried the designer and I see that in each corner of the frame is a blue square. I first turn OFF the maintain aspect ratio button. Then I try to SLIGHTLY adjust the position of the blue square so the verticals become straight up and down.

But...

PowerDirector won't let me move the blue squares A LITTLE BIT. It is like it has a "snap to" or a "magnetic" feature where it either doesn't move OR it moves further than I want it to.

Am I missing something? I just want to make the scale of the top of the shot a bit wider than toward the bottom of the shot. But I can't seem to make subtle changes.

Thanks in advance.