The real question is why Squarespace makes designers jump through so many tedious hoops like it's 2010.
Just offer a completely obvious and simple toggle in section settings that allows me to display it on desktop or mobile like every other template builder has for over a decade!
That's still woefully inadequate for truly useful functionality, but at least it's not forcing people to divine block IDs via browser inspection and then enter CSS that is far removed from the content and easy to lose track of, especially when having to do it a lot for an entire site.
Arg, so annoying that I have to patiently explain this in 2024.