[Feature Request] Keep highlight on currently active location in file tree

[shiltemann]

Is your feature request related to a problem? Please describe.
Sometimes I have multiple assays that are very similar, and want to be able to double check which one I am currently looking at.

Describe the solution you'd like
In the file tree, highlight the table/location I am currently looking at

Additional context
For example: I was unsure if I currently had my WGS_longreads or WGS_shortreads assay open in the main window. Would be nice if in the tree on the left the currently opened table/file/folder was higlighted.

When you first click on an assay it is highlighted in a darker gray, but once you navigate away from the main metadata tab, this highlighting disappears, would be nice if it stayed highlighted:

[JonasLukasczyk]

Added in 0d4e71b