Ooh by the way thanks for the offer for the component thingy but I can make my own reveal modal using just pure CSS or a mix of CSS and JS, unfortunately still doesn't make it better it must be my pc and my working times,
I am going to dig out site designer 3.5 and give that a go I seem to remember one of the earlier versions didn't lag but I can't remember which one.

Yes. I see this often. Irrespective of the framework being used, or indeed frameworkless sites.
I've seen the effect speed up if I make a lot of edits in a short time. So I am wondering if it has something to do with the undo queue, and even indexing the undo queue.
It certainly has nothing to do with resources (CPU, GPU, RAM) as these are plentiful and barely touched. It also happens on different OS (Win10 and Win11).
I feel it has something to do with a ballooning data collection issue in the software itself.