The only way I’ve found to do that is to create a Group. If you add the step(s) to a Group and then open the Thumbnail Editor for the Group you can resize the the green box, and even change the width and height independently of each other.
Hi @kori.leblanc
Richards solution is a great one if you are looking to have full control over an individual thumbnail, or a group of thumbnails.
If you want to permanently want to decrease the size of the green box (the thumbnail crop) you can do so in the recording template, this will make so all your past, present, and future recordings will have smaller thumbnails.
have a look at the attached PDF :)