Unfortunately there is no documentation about writing these scripts and any information about writing to the preferences file from within LR is locked deep within the product itself. The restart feature is much easier to access and (counter-intuitively) safer to use. I would be loathe to try to write a script to do what you propose because of the risks of corrupted preference files, LR crashes, etc. Strange that such an innocuous request could be so fraught with danger but that is the way it is.

The closest you could go is on Windows to write a script file that updates the line in the preferences file to set backup to the next run, then starts LR. Once again it would be dangerous to run this script from within LR because it writes to the preferences file while running and you could risk corruption. So there is no easy way to do what you ask unless you have two LR boot scripts, and call the correct one depending upon whether you want to backup now or backup at the next regular timed interval.

I set the option to “next time LR starts” and then run the script, go away and have a coffee. When I come back LR is running again.

Actually it would be great to have a script that sets the catalog preference and restarts in one step. Where do I go to find out how to write scripts?

I have not seen much of a problem with LR slowing down – but then I don’t use Web Galleries. Memory leaks!

You will also need to follow the remaining steps to install the plugin, but steps 4) and 5) are the critical ones for enabling the Scripts menu.