When developing components/websites/app UIs in actual code, the concept of percentage sizing has long been standard. I would really love to see this come to Figma.
Why would this be helpful?
Percentage sizing is an incredibly powerful tool for responsive design. If you could specify percentages, components and frames could expand/collapse as needed depending on the frame size (i.e., mobile, tablet, desktop).
How could it work?
I imagine that when you input width/height values, you could add a percentage and the hight would then become that percentage of the parent containers size. (i.e., Frame A is 400px wide and contains Frame B. The Size of Frame B is input as 75% and now Frame B’s size is calculated as (Frame A x 0.75). Additionally, including this option in the auto-layout padding/spacing inputs would be amazing. For auto-layout, the percentages would simply be calculated as (current frame W or H x %).