What visualization mode is that you could not set up in Slicer?
You can save the whole image as well.
Yes, of course. You can have unlimited number of volumes, segmentations, segments in the scene and you can export all of them to files.
Slicer has many tools for spine segmentation.
For example, using classic tools, you can quickly segment the entire spinal column (each vertebra in a separate segment) using Grow from seeds effect, and filling internal holes using this code snippet.
There are also several fully automatic neural networks for spine segmentation. There is a pre-trained model for entire spine segmentation in MONAILabel, but you can also train your own network for segmenting a single vertebra.