http://b2evo-archived.waffleson.co.uk/2007/11/playing-with-relations/

you couldnt find it because the way b2evolution handles its extensions sucks... even if the authors does not care to categorize or update info for those, the moderation should

Yoг don't need a separate plugin for it. Use a Universal items list widget with "Follow Main List" option selected.

I don't know if it works for single post though.

Does anyone have any alternative methods?

The Universal List doesn't work in the way I'm looking for and the AM Related Posts widget absolutely destroys the code on my website, making it unusable.