Back button to go up in blueprints

Similar to what is implemented in the Codex, the back button also navigates 'up' in blueprints.

You can easily go back by clicking on the parent folder in the breadcrumb trail at the top.
In your image example:
(Home Symbol) / Kayser's Smelting Furnaces / Iron / Accessories
If you are currently in "Accessories", just click on the word "Iron" to go back one.
Or you can also go back two by clicking on the words "Kayser's Smelting Furnaces"
Or you can go back to the root by click on the little Home symbol.
That is what breadcrumb trails are for. (This works in Windows File Explorer as well).