When using a single-line input, all characters are interpreted literally. This means, that instead of interpreting the backslash n, or "\n" as a new-line character, it will instead appear written out. One place where you might run into this is in setting parameters in the API Connector.

This is intended behavior, because it makes it easier to communicate things that are commonly escaped such as quotes, backslashes, etc. That said, wherever we have multi-line inputs in the Editor, you should be able to enter actual line breaks by entering them directly (enter to create a line) - and those will indeed be escaped under the hood into "\n".

A workaround to this behavior would be to use the boolean :formatted as text modifier, which gives you multi-line inputs. Therefore, even if you are faced with a single-line input, if you use a dynamic expression such as "Current User is Current User:formatted as text" and write multi-line literal values in the value for "yes" (since Current User is Current User always evaluates to true), this will allow you to have a multi-line value in the single-line input.