My keep right here is essentially a multi-floor perspectives map (needs some zooming in):

Do note that it can be pretty confusing handling the floors. While it is perfectly doable, Perspectives itself doesn't really know what a floor even is, it just works with surfaces. It is up to you to position those floor surfaces to make the illusion of floors look right.

No, there is no way to specify that. My approach would be to use the node edit tools instead. Now, you can't do this with them either, but you can easily calculate node positions to make this possible.

This is based on the fact that if you add a new node between two nodes, you are basically adding a triangle to the landmass, defined by the lines between the two old nodes and the new one. And the size of said triangle depends on the position of the new node, and can be calculated doing a bit of trigonometry.

Same if you remove a node, you are basically removing a triangle from the landmass (or adding one actually, if you are adding or deleting a triangle to the total depends both on if the angle is acute or obtuse, as well as if you are adding or removing a node).

It is the same command which is triggered no matter if you use Ctrl+C, pick from the menu, or the button right click. All of that are just simple shortcuts to the same command.

But for copy, it is important do follow the advice from @Wyvern about waiting till the command actually finishes and the selection indicators disappear, only then is the command done and the contents on the clipboard. And equally important is it to actually finish the command, a lot of people forget to pick the requested origin point after hitting Do it, but if you leave out that part, the command isn't done, and nothing will be copied to the clipboard. (Always pay attention to the command line)

I think you used the wrong button. In the video, Ralf used Change Properties, but you write Edit Properties in your post, and that prompt is indeed the expected one if you use Edit Properties.

The change Properties and Edit Properties button do look a bit similar, so they are easy to confuse.

Looks like there are a few .symfill files missing from the install, so it defaults to the standard escarpment config, and the default there is a line symbol....