Hi Del,
Excellent! Happy to help! :)
The slider is there to aid with cleaning up your paperwork without disturbing your 2D/3D environment. If you have two fixtures stack on top of one another, or really close, you can move them apart so it is easier to read on your plot. You'll also notice when after moving a fixture from its current position, it will leave behind a shaded "foot print" indicating that it has not physically moved in you 2D/3D environment showing its intended location. However, it will move if the slider is in the OFF position.
Oh! By the way: just a double click on the fixture, or address tail will pull focus to what you want edited. Easier than using Ctrl.
Be sure to check out this tutorial from Lars Wernlund. It is from Capture Polar so you will see some missing features (no little slider), but it's still very informative.
https://www.youtube.com/watch?v=_ziyDNuZ4wsCheers,
Johnny