So I think Layout has come a long way in the last few updates. Still, updating the model can take a while. So I suggest the following:
Incremental saves. If sketchup were to save in a way that only added the one line that was changed to that particular save, then Layout logically could update the model in a microsecond, instead of reimporting the whole thing and re-render the whole thing.
Some multi-threaded stuff in Layout. I know the whole old discussion of multithreaded limitations in CAD software, but still in Layout, navigating the page, and changing to another page, could probably be another process than rendering the page after a model update.
And also, when “open with sketchup” is selected in Layout, the model is automatically updated. But that starts once one goes back to Layout. Would it not be possible to save a few seconds if that updated in the background ?
And why do you have to repeat that “Open in sketchup” , for a model that is already opened, in order for automatic updating to occur?
Maybe that’s a Mac thing? On Windows once the SU file is opened from LayOut, you can go back to the opened SU file to make updates. When you save and return to LayOut the updates get displayed. No need to “Open in SketchUp.”
I should have made a slightly more complex model so the updates would have taken longer but this shows what happens on the PC.