424: Lost or deleted all the barlines

To delete or bring back (after deletion) all the barlines in a score try the following:

To delete:
If you select the very bottom (or top) edge of a barline (where it joins the staff) then you get a little blue box on the bottom (or top) of all the barlines. If you then press delete all the barlines will disappear.

To bring back:
To get them back you need to have another staff on the score which does have barlines (if you don't have one then press 'i' for instruments and add one). Then on the new staff click at the point where the barline meets the staff and you will again get a little blue box at that point. Drag this blue box towards the staff that is missing its barlines and they will re-appear and also be attached to the new staff.
Then either delete the new staff or drag the little blue box back towards the new staff which will then stop the barlines being joined between instruments.