Problem/Motivation
#1510544: Allow to preview content in an actual live environment added the the ability to preview content which is an invaluable tool to both site developers and content creators. In the context of that discussion search_index was concluded to not be part of a "actual live environment" so where excluded from previews. While accurate in the original requirements, not being able to quickly review what content will be indexed makes search development more difficult for developers and excludes a tool that could help content editors be confident the correct content is being indexed.
Steps to reproduce
Preview content with a search_index display mode. Search index is not an available display mode.
Proposed resolution
Allow search index to be select-able as a preview display mode.