How can I delete a layer/item in Google Web Designer?

I have been working for a few days now making a simple web page to be a basic cv/bio. I started by making my headers for the page and some simple animations when switching window sizes. After playing with adding some different colors in, I noticed that an asset I added, wasn't transparent(as I had intended it to be).

That said, I have tried to delete the item from the assets Library to no avail. I've tried removing all relevant keyframes, as well as trying to delete it from the Master Rules. The program will not allow me to delete the item, except from the Library, which does not affect the item on the page whatsoever.

I may well be missing something completely obvious and shall feel a fool when this is answered. Thank you for your help in advance!