Custom gradual dynamic text?

I am trying to figure out the best way to add custom gradual dynamic text. I’m typesetting a song, and the composer uses “increase” with a dashed line instead of “cresc.”

Ideally, I want to enter it as a dynamic marking, but it seems like the only way I can make text that also automatically can input dashed lines is using a tempo marking, but I only want this to appear for the piano and not the voice.

Here’s the original passage:
image

I’m afraid you can’t replace the cresc. text of a gradual dynamic, so you’ll need to create a custom line (via Library > Lines) that looks the part.