Keep the blank lines YouTube throws away.
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Questions about YouTube spacing
Why does YouTube remove my blank lines?
It normalises whitespace in descriptions, comments and community posts, and part of that is collapsing runs of empty lines. So a description you wrote with air between the sections arrives as a wall of text, which is why so many descriptions look worse on the page than in the box you typed them in.
What does this actually add?
One invisible character, U+2060 WORD JOINER, on each line you left blank. That line is then not empty, so it survives. The character has no width and no line-breaking behaviour of its own, so nothing visible changes.
Most guides say to use a zero width space. Why not that?
Because U+200B ZERO WIDTH SPACE is classified as whitespace. Some of YouTube's surfaces trim it, so the fix silently stops working, and because it is a space it can introduce a line break in the middle of a word. The word joiner is not whitespace and cannot do either.
Will it break if I run it twice?
No. The tool removes any joiners already present before adding them, so pasting a protected description back in gives the same result rather than stacking invisible characters.
Is my text sent anywhere?
No. It runs in your browser with no account and no network request.
Does this work in a video title?
No, and nothing does: a title is a single line and YouTube does not allow a break in it at all.