xbRefs Plugins Package contains two plugins - xbRefs - Content and xbRefs - Button - which form a replacement (with many improvements) for the previous xbFootnoteTag package. 
xbRefs - Button is and editors-xtd plugin which adds a button (on the admin site only) to TinyMCE or JCE editors to insert a shortcode {​xbref...}  for a reference footnote or popover.
Of course you can also insert the shortcode manually, but the button enables you to easily select a tag to use for the citation, enter text, choose whether to generate a popover or footnote, whether to trigger the popover on hover or focus, set the footnote number, and also will highlight the shortcode in the editor to make it clearly visible.
xbRefs - Content is a plugin that processes article text before display and replaces any  {​xbref...}  shortcodes with the appropriate content - inserting popovers and footnotes as required.
xbRefs Pulgins Package v2.1.1
24th April 2022  J3

Documentation  Demo Page

v2.1.1 Minor changes and bugfixes to both plugins.

New functionality includes new option to set a colour for links in the footnote area (default matches site setting), and the option to force popover to open with focus or click so that links in the popover can be clicked now applies if there are links in the description as well as to com_weblink urls. 

The shortcode at its simplest consists of  {​xbref tagid="17"}text{/xbref}  which will use the default options to display the tag with id 17 , using "text" as the trigger area for the popover  and inserting a reference number for the footnote.

Shortcode highlighting, like this  {​xbref tag="17" disp="both" trig="focus" addtext="to be appended to the description" } click text {/xbref} for example, makes it easier to find shortcodes in the body of text when editing an article.
That example renders like this click text[1]

For more examples see the Demo page

The content plugin allows you to either use a built-in css file to style the popovers and footnote area, or you can specify foreground and background colours to be used, or a set of your own class names for the various elements.

For further information see the xbRefs Plugins Documentation page

References & Footnotes
  1. Tainter, 1988 : Joseph A Tainter, The Collapse of Complex Societies, CUP 1988
    to be appended to the description

You can also use the shortcode {​xbref-here}  to force insertion of the footnotes so far in the article at this point (as above) and then any subsequent[2] footnotes will appear at the end (or at the next {​xbref-here} shortcode if you include another one.

Admin management of references in articles will be possible using the xbRefMan Component - beta release now available


Improvements and bug fixes

  1. v2.1 - Ready for use with xbRefMan Component
  2. v4.0 - Joomla 4  version (which will probably never happen)

... please report any bugs or problems on GitHub

Possible New features

  1.  Ability to define new tags from within the button interface - currently you have to have created the tags before inserting the shortcode.
  2. Ability to use the button to delete an existing shortcode and any associated highlighting.
  3. Ability to specify your own css file location for styling.

 ... suggest your own ideas on GitHub 

Changelog - click here


References & Footnotes
  1. Subsequent Reference : This is appearing at the end of the article