I use scale-dependent symbols for mapping (rendering Openstreetmap vectors as it happens). For instance paths show up when zoomed closer than 1:50000, but only roads show when zoomed out.
The rules for rendering are defined to make mapping usable on a monitor screen.
When printing my needs are different - the paper is bigger than the screen so it doesn't follow that the same rules should be used to define the rendering.
In another application I use it is possible to instruct the print layout to render the map using the rules normal for a particular scale even though actually physically printing at a different scale. For example I may want to render the map using the rules normal for a 1:50000 map, but because I want to squeeze the map onto a smaller piece of paper I need to actually print it to be actually at 1:100,000.
At the moment every time I change map extent or scale everything remains connected (changing map extent changes scale changes rendering style etc etc)... so the only option I see is to re-write the complex qml files I use to define rendering styles, so that I have one set of styles for printing and one for on-screen use. Am I missing something? This will be an extremely inefficient way to work.