FYI - Posting workaround for Chrome browser here.  I have to give credit to @Timothy Cameron

His page here:

 https://medium.com/@timcameron/expanding-all-in-confluence-db0d3cd711f0

Needed to "tweak" his script since the class name changed:

Edited the script slightly for the expand class:

javascript:(function()%7B%24(%22.css-15263az%22).each(function()%7B%20%24(this).trigger(%22click%22)%3B%7D)%7D)()

Bold for emphasis.  Not sure if / how long that will work, but it is working for me because the "inspect" shows that as the expand class.

I would love to know this feature is being actively developed somehow and will be released in the next major release of confluence. Pretty please?

This seems like low-hanging fruit - low effort with high payoff value.  If it can be done in a browser shortcut in a one-liner javascript, please consider adding this as a config option for this native macro or as a related macro that can be added ad-hoc to any page with Expand macros.    Defaulting open/closed in addition to "add Expand/Collapse All" button would be very useful to many.

"Largely covered by" doesn't necessarily mean covered by. The scope of CONFSERVER-27077 is the default behaviour upon page load.

This problem statement (searching inside expand macros) is largely covered by CONFSERVER-27077: Option to display expand macro expanded/collapsed on page load