The link I posted says you can merge to the top: “Shift+Enter: Adds the source note at the start of the destination note”.
It’s not obvious, and I don’t know how you’re supposed to do it on mobile. I thought I remembered it having a visible option but I just tried it on my phone and that’s not the case.
Actually you might be able to just do Shift+Enter on the on-screen keyboard — I think I might have done it before.