I did test that in Chrome and Tampermonkey with success ...
Ok, Firefox 62 & GM 4.7 using windows 10
There's a save icon to the top right of the edit window.
Note the attachment is as a word document - FT won't let me attach a .js or .txt file.
... and I get at the top "Error: Failed to complete http request". However the links appear and I was able to get through to the booking page with a DL routing.