I must have done this a million times before, but another senior moment is impeding my effort this time. All I wanted to do was to provide different lyrics for the upper and lower voices here, and imagined that what I’d always done was select the upper voice, use Shift-L in the usual way and then use the Properties panel to move the lyrics above the stave. Then (I thought) I used to select the lower voice, input its lyrics, and that was it. This time, this didn’t work - the lyrics for the lower voice include an extension line - needed in the upper voice but not in the lower - which I can’t persuade to disappear, and in any case I can’t remember encountering this complication before in similar circumstances.
Incidentally, the Shift-L, Shift-Up arrow routine mentioned in the manual has a completely different effect to the description, in that it just adds every item in successive staves to the selection, notes and all. How should I have gone about this?
In the meantime I found that I had no problem with a similar situation later, so I went back to this, and accomplished the task with no problem (before I saw your messages about the colours). Some of my synapses were evidently misfiring previously.