When a sales rep is manually moving a deal between stages, we often need to make sure that they're capturing certain data. So if they finish a sales call, we might want to know their confidence level, or the products/services they're interested in, etc.
Here's an example of how it works in HubSpot: https://share.vidyard.com/watch/z9pfGzPc9umdQznYSRp1Wv?. If you could recreate this type of functionality, that would be awesome.