It took me a while to figure why I was repeatedly being confused when handling branches, then today I found it: In SourceTree (for Mac), on the left hand side, in the overview for the branches, not only the currently switched-to branch is shown in bold font, but also the one which is currently highlighted with the mouse pointer.

The currently switched-to branch is otherwise only marked by the slightly different icon. The currently mouse-highlighted branch is otherwise also marked by it's colored background highlighting.
The mouse-highlighting stays (tho shown in gray background, but still boldface) even when working in other parts of the application, for example the log.

Generally, the less important information of which branch I have previously clicked by mouse is optically dominant over the more important information on which branch I am currently working on.
Took me a while to understand that my brain was mainly confused by the bold typing of the string.

I have attached an edited screenshot which I hope helps my explanation. In the two different cases, I have clicked from one to another branch. First, the master branch is selected, then the NO-Manueld-cruft. You can clearly see that the last clicked item is shown in bold font.
Please note that the branch I am currently working on (in these pictures) is neither of these branches. The current working copy is on MONT-85.
In both cases, the most dominant information in the picture is the least important one, at least as long as that highlighting is persistent over activities in other parts of the application.