Certain scroll bars within the Editor while on a Mac have their directions reversed. i.e. The 'World Outliner', the 'Details' panel within a 'Blueprint.'
The suggested workaround I gave to the user was to disable the 'Natural Scrolling' within the System preferences of his Mac. However this only worked for scroll bars and did not fix them all.
There is also no option to simply invert the scrolling within the Editor.
1. Create a Blank First Person BP Project.
2. Click in the 'World Outliner' and attempt to scroll using the Trackpad.
3. Even if you Enable/Disable the 'Natural' scrolling within the system preferences of the Mac, some of the scroll bar directions will be inverted/reversed.
Head over to the existing Questions & Answers thread and let us know what's up.