I partly answered questions already.

1. Yes.  Always show.  Fix delay at 80 until we decide on something better.

2. No.  Max should be enough.  I once printed over 500_000 short lines to see if scrolling remained responsive.  It did.  I could have set min to 1_000_000 for that experiment.  Am I correct in presuming that only one block of output, between code imputs, can be squeezed?

Converting extensions to features mostly removed the option to omit features.

3. No, if not gone already.  I don't want to proliferate keyboard shortcuts, at least not until we get rid of some that must be nearly unused.

I want to make revising the use of keys within output blocks a separate issue.

4. Maybe nnnn chars would be better.

'a'*1000 currently wraps to 13 80-char lines.  (This would change if we add horizontal scrollbar, as has been requested.)  The viewer does not wrap.  I think it should as there is now no way to see entire line.  Or it needs a scrollbar.  Viewer is modal, but does it need to be?