One of the words is missing again.
Why not "two waitresses working in the restaurant?"
It needs a verb to be a sentence. This would be just a sentence fragment, say of, Two waitresses working in the restaurant saw the thief enter.
Could you use the word ' 'servers' in place of waitresses? Server is more commonly used in metropolitan cities in the US, at least on the east coast
Is there a non-gendered term for this profession? Such as, police officer instead of police man or police woman for example