There are buttons to bold and highlight in yellow, but none to italicize? Is it possible?
No, only what you see is available. Put it as a suggestion, if you like.
Hello. I know I’m a year late!
Anyway, you can italicize the font, with the normal shortcut we know CTRL+i. Even though it won’t show up when you’re actually editing, when you Save the description, the new changes are shown when you go to the Gig Description page.