There should be a preference option to turn on or off "show % in register"
In a split transaction, there's a checkbox for "show %". I'm suggesting that option should be controlled in the preferences/ register preferences. I have to check the box every time I want to see the %'s. It should be on always or off always. If it's off always, then you should be able to check the box for maybe one transaction.
[Edited to add more context]