In the end, changing the value by mouse in fractions of certain units (e.g. em/rem) is even already integrated in some areas, like in the font section.
Would be great to have this in other sections like the margin/padding section too.
Not entirely sure why we never did extend this function to all fields.
Thinking about it, reviewing your other thread and now that default units now available, maybe it’s a good idea to also allow users to specify a specific step as well if they want to override the default.