New to Storyline: Playhead issue

I have exactly this issue as well. Using cue points is a good start but doesn't solve the problem when you need to POSITION an object on the screen relative to something in the video. For example, I'm trying to insert a zoom region so that I can focus on a particular dialog box that appears halfway through the video. I need to be able to stop the video and have the video stay on the current frame so that I can resize and position my zoom region correctly. 

Often if I preview the slide from timeline, hitting pause will do just that - you are at a certain point in the video and can put shapes, whatever on the screen and you are seeing the status of the slide at x seconds. This has always been very buggy though. sometimes it works, sometimes you have to wait an eternity for Storyline to catch up, sometimes it just doesn't work at all. Even when it does work, it is sloooooooow, so adding objects to make interactive videos is a pain in the you-know-what.

So maybe asking the question differently: how do you advise positioning objects over the top of the video, for example to position a zoom region or maybe an arrow that is pointing to something that is only visible at 5 seconds in?