First example is

Joomla Admin -> Content -> Media = expect the media manager to open and the left menu to still be on Content -> Media highlighted.

Content -> Fields -> Select category in the drop down -> Select articles in the dropdown = menu collapses

Home Dashboard -> Click Remove or Export in Privacy Dashboard

Expect menu to be like this

But its still collapsed like this:

Home Dashboard -> "No urgent privacy requests" green square

Basically anything under System menu item, that doesn't have a corresponding left menu item component, should also keep the System menu highlighted... maybe.

Any page where you click Options... So Content -> >Articles -> Options... the left menu collapses, instead of staying lets say on Articles..

basically any URL that uses a filter as a url param

http://127.0.0.1:4444/administrator/index.php?option=com_newsfeeds&filter[category_id]=5&filter[published]=1&filter[level]=1

This link is found by clicking the number under the tick on the News feeds categories page

Leads correctly the newsfeeds component, but the menu collapses and doesn't stay open at Newsfeeds

When you get a Private Message (from Mr User Action Logs)

then you click to read it:

Components -> Smart Search -> Content Maps -> Click the number of published indexed content (green box here)

Sorry about the colour scheme...

Then you see left menu collapses

I've found the root problem - hopefully during my sleep I will dream up the solution

@PhilETaylor please test #34465 it addresses everything apart from categories which is a different root cause

Thanks.

Ive tested this today, its not perfect (as you clearly state) but is a million times better. I'll close the #33590 and document any left over issues overtime