What are Kékulé numbers? I saw them in the menu and don't know what to do with them.

Kékulé numbers are explained in great detail on this website:
Kékulé numbers

In MacFamilyTree, you can use them to group close relatives in the persons overview list, for example.

In the left-hand column, click Edit, then Persons
The overview list will open
Right-click (ctrl-click) the person you'd like to see the close relatives of
Choose "Calculate Kekulé-Numbers" from the context menu
Click the coggwheel button in the bottom right corner
An Options window will open
Make sure that "Show column for Kekulé Number" is activated
Back in the overview list, click Kekulé in the head row
That field will be highlighted blue and the overview list will be sorted by Kekulé numbers

Support