I have read previously about git flow models for various stuff and wanted to make use of them.
Clicking the Git Flow button on the toolbar I was presented with some prompts I wasn't totally sure I understood. In a rare display of convention, I actually clicked (?) to get some help.
SourceTree v1.5.7.1 reported that it was unable to open help.
As others will be in a similar position to myself grappling with the potential cognitive complexities of flows, this is surely a bug that should be resolved.