Allow Percentages in Variables

Please can we get percentages for variables? We can use percentages manually, but we can’t create a percentage as a variable. This would speed up my design to dev process tenfold, and considering we can already use percentages in the design, why disallow it in variables?

An example is I want store values for line height and letter spacing as percentages which behave responsively/dynamically, so when creating type variables I don’t have to do manual calculations, store 10+ letter spacing/line height values based on which font size they will be used with and hope I never change the font size variable in the future.