These are all tightly tied together. The setting of "The Waltz" is a dance—it is a location, a time, and an activity, all at once. The conflict is between the internal desires of the female main character and the demands placed on her by external society. She wants to have a good time, do what she wants, etc.—but she also has to put up with the literal kicks of her dance partner, and his irritating habits. As for plot, there is only a limited, looping plot: she wants to get through the dance, she does, and yet she's still trapped in the dance.
On the surface, Parker's "The Waltz" revolves around a woman who must decide to decline or accept dances with various suitors. The dance hall is the setting. We know this from the opening lines, as we hear both the external and internal dialogue of the woman. For example, she thinks, “(M)ust this obscene travesty of a dance go on until hell burns out?” This can be viewed both literally and symbolically.
Literally, she is at a dance hall. The symbolism is in the "dance" that men and women do, often without satisfaction. As she accepts a dance invitation, the world weary protagonist laments, "“When you kick me in the shin, smile” (1617). Again, there are both literal and symbolic overtones. Literally, her dance partner is a klutz. Symbolically, the dance men and women do sexually and emotionally is often devoid of grace.
The conflict is that the protagonist longs for truth that she will not find. She wishes that at least the phonies would acknowledge that they are being phony! It would be a start…
This is the central conflict. How do women or men find satisfaction in life dance that is often shallow? Are we doomed to an eternity of mediocrity, dancing, as the protagonist does, with characters like "Double-Time Charley," not caring about fulfillment anymore "after the first hundred years"?