Can I say "stuffs" as a plural noun?

Solution 1:

There are several cases where collective nouns are pluralized. "Fish" can mean one fish or several fish, but "fishes" usually refer to groupings of different types of fish - so it's a pluralization of the collective, not of the singular.

This could be generalized to this case as well. "Stuff" is a collective noun, but "stuffs" would probably be understood to mean distinctly separated groups of stuff.

Solution 2:

"Stuffs" as a noun is incorrect. The reason it is different from other collective nouns is because it is also a mass noun. Words like rice, water, smoke, and cement are all mass nouns (or uncountable nouns). You could say "several piles of stuff" to make it plural, but not "several stuffs."

As others have said, "stuffs" is also a verb (present tense singular), so the spellchecker won't count it wrong. Hopefully, a good grammar checker would.

Reference: https://en.oxforddictionaries.com/definition/stuff