Is there a common abbreviation for "with or without"? e.g. _w/wo_ or _w/w/o_

If this is for use with a limited audience, especially one which can be directed to a glossary of abbreviations, then w/wo could be a decent option. I've used it myself, and seen it used, so it wouldn't seem strange to me. But as usual, context matters.

It depends how much space you have, but I’ve used ‘w±o’ or ‘w∓o’ before to mean ‘with or without’ when space was exceedingly tight. You wouldn't need a slash after it, but could use it if you’d like.

Like suppose the whole gang is starving one hot summer afternoon and so you tool on down to your local Doggie Heaven™ drive-in restaurant. When you get there, you notice that their menu advertises:

? Baskets come w/fries+slaw
? Naked dogs come w/o buns
? Fries and rings available w±o/salt

And so you order yourself up:

1 redhot basket w/rings
1 bratwurst basket w/kraut
1 naked polish w/chili
3 redhots w/o onions
1 knockwurst w/catsup

Or at least, that’s what your curbside food attendant writes down on their tiny little notepad, where space is dear and time of the essence.