I agree, I would like to see the open accordion tab(s) remain open (and width-expanded?) on page reload after clicking "Save".

for width-expanded : only if we expand width :).

For such system : i use # with JS solution, and sometimes :
#tab1/tabintab2/tabintabintab3

:)

Principle is to add the #to the submit url, and the save url must be the same url. (more easy when using directly $_POST without any url (take actual url)

@DenisChenu - "for width-expanded : only if we expand width" - yes, of course :)

could you please reopen it as a feature request?

Moved to Feature