Chrome & Firefox extension for Notion to add 20+ features like sticky outline, small text & full width by default, hide comments & help button, bolder text etc. Download here: https://gourav.io/notion-boost
I came here to request the same. This is the one feature I really miss in Notion (and have requested them to include). I use Notion as a zettlekasten tool and I click show backlinks all the time.
Expand backlinks for all pages by default.
Thanks!