Feature request: Allow to hide top bar

**Is your feature request related to a problem? Please describe.**
Even though the top bar is very thin and nice, it could be interesting to have a way to hide it and leave a little more room for the main application.

**Describe the solution you'd like**
Probably the best way is a "minimize" button. Maybe a little change of the UI is required to leave space for the button when minimized.

Maybe remember the status of the button, or also an option to always start with the bar minimized?

**Describe alternatives you've considered**
A "close" button would be easier to implement, but it's not ideal for the user because there is no undo (without reloading or something).

**Additional context**
Add any other context or screenshots about the feature request here.

No files, tests, or entry points are named. Start by locating the top-bar UI and its layout/state handling, then determine how a minimize control affects the available application space. Done means the bar can be minimized and restored without reloading, with any persistence or startup option agreed before implementation.

Written by the indexing model from the issue text.