This has to do with the new configuration GUI. I cannot enter a new line (Return symbol) in the Insert/Paste/Type text action in the new GUI. If I change to the old GUI it works fine. When I press the [Return] key when typing the text in the configuration box of the Insert/Paste/Type action all it does is highlight the line of text I just entered.
You need to press option+enter (this works everywhere in macOS btw)