The Copy Visible Lines item in the Fold menu copies the selected text to the clipboard. There are two key differences between the Copy Visible Lines command, and the regular Copy command in the Edit menu.
If the selection is not rectangular, and certain lines are only partially selected, the Copy Visible Lines command will copy those lines entirely. The Copy command copies partially selected lines partially.
If certain lines were folded, the Copy Visible Lines command will not copy the lines that were made invisible by the folding. The regular Copy command does copy them.
Text copied by the regular Copy command does preserve folding ranges when pasted back into EditPad Pro. All the text will be pasted, and will remain folded under the pasted folding range. If you paste into another application, then all the text appears without the folding range.
Text copied by the Copy Visible Lines command is always pasted without any folding ranges.
Fold|Delete Folded Lines