Uploading a new extension is fairly simple, but assume an older version of the extension exists and you want to publish a new version that breaks compatibility with all SketchUp versions except the current one.
As we know, a significant amount of the user base is on 2016 or even 8, so there is an interest besides of historical reasons to keep the older version available to those who access Extension Warehouse from an older SketchUp version.
Can an extension page offer multiple downloads? (or even distinguish which to show depending on SketchUp version?)
Should I upload the new version as its own extension (e.g. “MyExtension 2.0”) and thus bloat the search results? This way users who use the old “MyExtension” in the latest SketchUp would not learn that they can update to a new version.
Should I update the existing extension page “MyExtension” by uploading the new version, changing requirements and pushing the version number to 2.0; then upload a copy of the old version as a new extension “MyExtension 1.0 (old version)”?
What kind of notification do users of an old SketchUp version receive if one of their extensions is updated and requires a newer SketchUp version?