Hi @RonB RonB,
I am fairly sure that it is not possible to have that amount of control when generating .gifs from bubble plots or other animated visuals in JMP. The capability to save as gif is fairly basic in JMP. I think it is really only intended as a quick and simple way to generate gifs for pasting into PowerPoint (or other).
You can request new features in The JMP Wish List. Have a look - someone may have already requested these options.
Personally, my solution would be to use dedicated screen capture software that has the kind of editing options that you want. I use Camtasia but I am sure there are many other options, including freeware.
I hope this helps,
Phil