After Yutaka’s steps, if you still wish to add “>”:
Select the lines.
Use “Select Beginning of Lines” command.
Type “>”.
You can record the whole procedure as a macro.
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Actually there are quite a few ways to do this in EmEditor.
▼ Here’s the most simple/economical way I think, to get an almost same result:
Use “Wrap by Window” command.
Resize the window to the wanted width. (Show and see the ruler at the top of the view.)
(Or use “Wrap by Characters” command instead of the above two steps, if your “Normal Line Margin” setting is 80 (default).)
Select the lines you want to convert.
Copy.
Use “Paste in Quotes and Newline Characters” command.
▲ You can find the commands and descriptions by searching in “Quick Launch” (default key: Ctrl+Q) if you don’t know where they are.
▲ You can assign shortcut keys to the often-used commands/macros.
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▼ Another simple way, to get an exact same result as you presented:
Use “Wrap by Characters” command. (Default = 80.)
Open the current configuration properties:
Wrap:
Add a space in “Not Allowed at Line End”.
OK.
Select the lines you want to convert.
Copy.
Use “Paste in Quotes and Newline Characters” command.
Compare the results in my screenshot:
i.ibb.co/C8Lhx2m/Em-Editor-Wrap-By-Char-Q-NL.png
Actually your max line length is 79. ;-)