Maybe by adding a 'sub-branches' tab when the current branch contains sub-branches (well detected by 'branches' command of BzrTools) which will show an embed 'Browsing' view.
In addition, an expander on global 'Browsing' view to expand the folder or branch and show sub-branches and sub-folders containing sub-branches rendering something like the attachment.
Maybe by adding a 'sub-branches' tab when the current branch contains sub-branches (well detected by 'branches' command of BzrTools) which will show an embed 'Browsing' view.
In addition, an expander on global 'Browsing' view to expand the folder or branch and show sub-branches and sub-folders containing sub-branches rendering something like the attachment.