With the Minimal Mistake theme one can define side bars. Is there a possibility to highlight the choice you did in a side bar to know which part you are currently reading That would help a lot the navigation. This is well done in the TOC on the right but not on the side bar on the left.
The sidebar on the right is generated automatically from headers in main content so it can have some smarts behind it to do the highlights. It’s using
ids on the headers that are auto generated by Kramdown as waypoints to target the links against and know where you are on the page to add highlights.
That doesn’t exist for the left nav since those are built manually by whatever YAML you add and doesn’t have the same relationship with the main content. I don’t think there’s a one size fits all approach I could bake into the theme to do it for you.