Firefox doesn't explain how to do this at all, but it is possible. Make a bookmark with the URL you want, and set the keyword to whatever symbol you want ti start it with.
For example,
Name: Scryfall (or whatever you want)
URL: https://scryfall.com/search?q=%s&unique=cards&as=grid&order=name
Keyword: s
Then type "s Birds of Paradise" to get the result you want.
I did the same with Reddit and it worked on my end. If it doesn't work for you I'd be happy to help you figure it out.
It's also possible on mobile, and it's actually even easier: Settings>Search>Default Search Engine>Add Search Engine. Then you can type your search and choose the engine from a dropdown menu.
That makes no sense. Division is just multiplication by an inverse. There's no reason for one to come before another.