I remember using a version of Explorer that had collapsable hierarchical navigation on the left, as well as similar non-filesystem programs with a similar desig

I remember using a version of Explorer that had collapsable hierarchical navigation on the left, as well as similar non-filesystem programs with a similar design and do not recall being fond of it. Especially on smaller screens it was easy for the left pane to become too small to fit the names of deeply nested directories, and then become too wide when collapsing them. To me at least that style is somewhat awkward and fiddly.