Re Turning lines on/off: Just making sure you know a bit about working with shapes:
• ensure you use two clicks not double-click
• select a group (rectangle + lines)
• select one shape/line within the group (eg. one line)
• change any property of that shape/line
• including Deleting it and moving it
• while remaining in the context of the group
OG works well (consistently) with levels, eg. a group made up of groups:
• one click to select outer group
• second click selects a group one level down or "in"
• third click selects shape/line inside that group
Thus, we have basic turning lines on/off by deletion or property change.
To change a shape/line off (truly off as distinct from deleting it), select everything (fill, stroke, text colour, etc) as white, with an opacity of zero.