discourse marker

No.

Anonymous Is the discourse marker 'you know' an adjective or adverb?

No, it's a clause where "you" is a pronoun and "know" is a verb. Some label such wording a filler which fills an unwanted pause in conversation.

Anonymous an unwanted pause in conversation.

I've always referred to that as an "articulated pause". [ umm, ehhh, etc. ]

unwanted pause

Unwanted by whom? In most cases, the speaker seems clearly to want it.

Clive

Cliveunwanted pauseUnwanted by whom? In most cases, the speaker seems clearly to want it.Clive

The gap-filler is wanted, the pause not, hence the filler.

CliveIt is often used as a device to soften a statement and make it less assertive, more tentative.

I agree but it doesn't exclude the gap-filling function.

CliveYes. But my point is that there is not always a gap. If the person wants to say 'you know', I see no gap intended.Clive

The "you know" is usually outside the syntax of the clause which it belongs to. That's my point.