You select a block by "dragging" a rectangle around it.
If even a bit of something is inside the rectangle, all of it will be part of the selected material.
It may not appear that you were successful, but if you move the mouse, you will see that you have "picked up" what was selected. (To get out of a bad selection, and put things back where they were: Press "Escape".)
If, having selected a block, you right-click, a pop-up menu will appear.
"Delete Block" works as you would expect. (Ctrl-Z will UN-delete mistaken deletions, if you do it right away, before doing other things.)
Copying a block may tie you up in frustrated knots for a bit. To do that…
- Select a block
- Right click
- Click on "Copy block". Nothing appears to happen!
- "Move" it. (The original will be unaffected)
- (Left) Click… which should "drop" a copy where the mouse pointer is.
(It is a little disconcerting when "nothing" happens when you click "Copy Block", but the "different" procedure works very well in practice.)
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