Currently the behavior works like this:
Normal mode: each panel I click toggles open or close. I open panels when I need them, I only close them when there are too many. Eventually I get too many open panels and I get visually confused or have to scroll way to much
Alt-click mode: I alt-click a panel and it closes everything but what I click. Essentially the alt is a shortcut to close all the undesired panels, again when too many are left open. Essentially the user-friendliness gets worse and worse until I’m forced to fix it.
Suggested behavior: Normal click option closes all the panels except the one you are using. If you want more than one open at once, THEN use the ctrl key.
-Using the ctrl key to add extended selections is already almost an industry standard.
-It keeps the panel column clean and compact, aiding navigation. In the 3D view it is WAY too long when open panels start accumulating. The current alt option is used to frequently fix a growing clutter. My suggestion will keep panels regions clean but give YOU the option to add more clutter (open panels)
-It can always be an option in preferences if someone likes the current version, maybe they use small fonts and like to visually scan the panel column.
-If you think about it, this behavior almost acts like vertically-stacked tabs, and I love tabs, use them all the time in my own GUI design.
Now I think this is probably a trivial programming task. If desired to complicate things an even better option exists: In addition to the above request, add an option to pin individual panels open (or closed)
BTW, the suggested alt-button behavior actually starts