> Is there a way to turn off the lines, apart from picking them out
> one by one and hitting the hide button?

There are 2 different types of lines - what Schbeurd wrote above applies to "Edge curves", which are the lines that show up at the borders of a surface. These are sub-part of a solid/surface object.

But you can also have regular individual curve lines that you drew with the "Draw curve" tools. I think you may be asking about hiding these regular lines?

Sometimes it is easier to select the reverse pieces, then do Select/Invert to flip-flop the selection.

The other thing that can help instead of picking one-by-one is to do an area select - this is when you click out in empty space and the drag a rectangle around things, this allows you grab a bunch of objects in one go.

The area select works slightly differently depending on whether you drag it starting from the left towards the right, or right-to-left. If you go from left to right, it will show a solid rectangle and only things completely contained inside of it will be selected. If you go from right to left, it will show dashed and things that intersect the rectangle in any way (not just completely contained) will get targeted.

So some strategic use of the area select can speed things up - you can often get an area that will grab a bunch of curves but doesn't contain the whole surface/solid (using the left-to-right method).

- Michael