Hi,
recently I noticed that 'delete all references' also deletes
statements even if they don't reference the line being deleted. (How)
can I prevent that?

I was working on a proof, and I had proven a small "lemma" I thought
might be useful in subsequent proofs, but later it turned out to be
irrelevant, so I wanted to delete it. Since it wasn't used at all, I
thought it wasn't a problem at all. But I was warned that deleting
this would delete 100 or so statements-- far more lines than the proof
of that lemma.

Regards,

Thomas