How do you remember what you put into the stack?

Like the I'm packing my bags game. I add or remove items one at a time and repeat the entire contents back to myself after ever amendment. I'm sure you could use method of loci or something, but repetition is good enough for me.

What kind of a representation does the topic have? Nothing special. Words, ideas, images... something short I can "think about" for a fifth of a second, then think about the next item on the stack as I'm mentally repeating them.

Do you remember the contents of the stack for long afterwards?

No. The stack is a trick I use during thick of a conversation or debate to not lose track of topics I'd like to return to. However, I suspect it primes me for better remembering conversations when I review (and log) them at home.