New measure

[charemor]

How do I add a measure in the middle of a page? The "add measure" seems to work only at the end of a piece.

[Peter Thomsen]

Use "Insert" instead of "Add".

Note that "Insert" won't work until a measure is selected.
The new measure will be inserted where the selected measure is (and the selected measure will be pushed to the right).

[Peaceful]

Right. It is in the Edit drop-down menu and is called Insert measure stack. This adds a measure to each staff.

Can one add a measure to just one staff? I mean, insert a measure to say, the treble staff, moving the rest along, but leaving the bass staff intact? I might have omitted a measure in one staff. The alternative is to insert a stack and laboriously move all other staffs to the left.

[miker]

No, you can't add a measure to a single staff. But it's not so bad to move the others. Click in the first measure you want to move. Shift+End to extend the selection to the end of the piece. Grab the first measure, and drag it to the left. Done.