It should not remove new presets. It would update existing presets if you had saved over the old presets.
I'm not sure what exactly you are looking for. Custom presets should not be removed when uninstalling or reinstalling the extension. If you are reinstalling DW or your hard drive, you should back up your designs by exporting and saving them. If you haven't backed them up and they don't exist then there may not be a way to get them back. If you think they were deleted then please post a support incident. They shouldn't have been so we would want to investigate how or when they were.