In the case of Occurrence <-> IFC Occurrence configuration, you will note that there are a "+" buttons available to the right for the configuration name;
...
These enable you to create "Sub" Configurations which you may want to apply to only Occurrences of specific IFC Categories.
Example:
To create a Sub Configuration which you would like to apply to only IFC Category “Walls”, select the "+" button within the Occurrence <-> IFC Occurrence Configuration, then select "Walls" as follows:
...
Once you click on "OK", a new (Sub) Configuration window will appear. Here, you need not (and cannot ) set up the "Key Attribute used for comparing" (your Main “Occurrence <-> IFC Occurrence” Configuration would have that already), but rather you can pick properties on either side and choose the direction in which you'd like the values of the properties to go.
...
The Category specific configurations will allow you to synchronize different data based on what type of object you synchronize. The result in the Attribute Configuration Settings looks like this, where there are established two category-specific configurations for IfcWall and IfcSlab;
...