Hiding the sheet the lights are on should deactivate them, so you could set up more than one LIGHTS sheet and split the lighting between those sheets to be able to have different lighting setups.

If you want to deactivate lighting, theoretically it's possible by opening the Global Sun settings (in the right click menu of the sheets and effects button) and turning the shadow transparency up to 100%.

I don't think the polygons were outside the edge of the map. The entities I deleted were symbols, I believe. You can paste symbols anywhere, and it's easy enough to do. I've found trees and mountains and all sorts in strange places where I must have mis-clicked at some point.

EDIT: The SCREEN is to hide the bits of symbol that stick out when you paste symbols on the edge of the map, or when you deliberately draw polygons outside the edge to counteract an Edge Fade, Inner sheet effect. It doesn't chop things off, but only covers them up. You will see what falls outside the edge if you zoom to extents and hide the SCREEN sheet.

EDIT2: The drawing tools used to draw things like land and terrain are often limited to the map border, which usually coincides with the inner edge of the screen. However, you can override that behaviour where you want the polygon to go over the edge.

Thanks - it was a team effort. Remy (Monsen) found the sheet before I got there :)

The issue would seem to be one or more of the nodes that were deleted by SIMPLIFY, though quite why CC3 didn't like those particular nodes is unknown.

SIMPLIFY is a keyboard command. If you type it and hit enter, then read the command line you will see CC3 prompt you for a distance. This distance is the minimum distance you want between the nodes of your line or polygon. So if I'd typed "10" and hit enter a huge number of nodes would have vanished from that polygon and none of the remaining ones would have been closer than 10 map units.

The reason I tried zero first was to preserve the drawing the way you wanted it if possible. If it hadn't worked I might have tried 0.1 next.

Another way to deal with redundancy like that is to add a couple more sheets with Edge Fade, Inner sheet effects on them and draw irregular patches of different grass textures on them.

You can convert the line to a polygon using 'Path to Poly' in the right click menu of the Fractalise tool. It looks like you might have a line width greater than zero, which will form an open polygon. Use Change properties to set the line to zero width and pick your fill, sheet, and layer.