To reproduce:
1. Create a git repository with branches organized in a hierarchical structure, such as AB/button-alignment. SourceTree shows this structure as folders.
2. Check out "develop" in that repository in SourceTree. Make sure you have no other local branches.
3. Check out AB/button-alignment. Look at the left pane. You'll now see the AB folder as expected in your local branch list, and you are actually currently on a branch thats in that folder. However, the folder hasn't been expanded for you, so its hard to tell where you are at all. Notice that none of the branches in the list are now bold (the one thats bold is hidden), so it looks like you are "nowhere" in terms of your repository checkout.

Expected:
When checking out a branch that will be in a newly created folder in the source list, SourceTree should automatically expand that folder, so its clear where you are.