I use dolphin Version 16.04.2. What I do: I enter some path in the right panel (detailed view, without collapsable trees), for example /home/myhome/.kde/ Then the path is not shown on the left folder-view panel, so it is difficult (not user friendly) to navigate in the hidden folder-tree. I know I could enable show hidden folders on the left panel, but this is not what I want in general. This is a special case, where it should show the currently opened hidden folders nontheless. Reproducible: Always
Can confirm with Dolphin 18.04. I think this might need an ugly hack to implement, but it'd still be a nice addition for everyone using the Folders panel.
Still relevant in git master.