Filip Jakobsen suggested a simple way of easily indicating where to focus currently is within a pane by applying a blue border to the top of a <Pane> when something is in focus inside of it.
I tested this out and I think it would be a nice addition to the FOLIO system.
One caveat though: I am using the ":focus-within"-selector which is currently not supported in some browsers – including IE, Edge and a few more. More info here: https://caniuse.com/#search=focus-within
I think it's okay to implement this even though it will only work in the latest browsers – mainly because it's not a critical feature and it is a simple change.
I uploaded a screenshot and a video demonstrating the style applied.