Bing Search’s sitelinks can sometimes be expanded to see sub-sitelinks, deeper level sitelinks. This is something Google experimented from time to time but something Bing Search does on mobile right now, at least for me.

Here is a screenshot of Bing with expandable sitelinks, as you can see, I clicked on the “images” sitelink and it showed me two more sitelinks within it:

I am not sure how long this has been live but Shameem Adhikarath noticed it earlier this month and posted this on X:

Forum discussion at X.