Good discussion.
For myself I prefer the SU16/17 trays over previous structure.
For navigating in my set-up which is one vertical tray of 7 panels,
I use Shortcuts to open a particular panel (eg: Preferences>Shortcuts>Windows/Show Styles) and a click on the header to collapse. So what I would like to ask for is the addition of a Shortcut = Windows/Collapse All, as an additional option to clicking on the header.
Best
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