Here is my scenario... I've animated V4 to sit... I've also animated her dynamic outfit. So she is now sitting with her outfit all simulated. I used 200 frames for this.
With the dress already simulated... Character sitting... But I want a new pose, maybe just shifting the upper torso, but I know the dress will need to shift too... Is there a way I can make frame 200 be the initial zero and animate a new pose... Then animate the dress with cloth effect from the new sitting position? I just don't want to have to start all over with re-draping and all that.

You can only have one simulation per cloth. You won't be able to start a second sim at frame 200. If your version of poser has spawn morph target, you can try to the first drape that way. It should work if you're not doing animations, turning it on and off as needed. If you are, you'll probably need to sim all of it again.

Unfortunately there are no logic way to do this. However a way you can do it is to export the final frame of the simulation as an obj file (Make sure you only select the cloth). Then import it again instead of the current cloth. Now the default shape of the cloth will look like the last frame and you just have to setup the simulation again, meaning just replace the old cloth with the new cloth you imported in the cloth room, all the settings should be the same. Also make sure that you reapply the textures after import.

It would be a very nice addition to Poser if you could actually set an initial starting frame, hope they add that at some point.

You can set an initial start frame for the simulation in the settings, same as setting the ending frame. But you lose any draping done before that.

At the frame where you are happy with the drape, use the Group Editor to spawn a new prop from the dress, then a new simulation for the new prop starting at the desired frame selected in the simulation settings dialogue. Delete or hide the original dress Poser will not include hidden items in a cloth sim.

You can also spawn a morph in the dress at frame 200, Then start a new sim with that morph set to 1. After the sim has finished, set that morph back to 0. (The 2nd simulation already takes the shape of the dress into account, so you to reset the morph.)