Description
When applying a stashed change, esp. when enabling the "delete after applying" option, we loose the information expressed in the stash message. This information will usually describe the stashed change. Thus, in many cases, the developer will want this very message (or a slight variation of it) to become the next commit message.
I'd suggest that SourceTree adds the message of each applied Stash to the current commit message (without committing the changes, just like it is happening now).