"The shampoos are next to toothpastes."
Translation:A samponok a fogkrémek mellett vannak.
It is about a location (where the subject is), not describing the subject. So, "vannak" is not omitted.
Why "toothpastes" (without "the") should be translated as "A fogkrémek"?
There is a definite article missing in the English sentence. I report it here because the 'report'; button does not provide an option to say 'The English sentence is incorrect'.