In the case of Item <-> Revit Family as well as Occurrence <-> Revit Instance Configurations, you will note that there are "+" buttons within the 2 sections as follows:
These enable you to create "Sub" Configurations which you may want to apply to only Families of specific Category / Categories.
To create a Sub Configuration (for the Item <-> Revit Family Configuration) which you would like to apply to only Revit Families of the Electrical Equipment Category, select the "+" button within the Item <-> Revit Family Configuration, then select "Electrical Equipment" 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 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. In this example, we will rename the Sub Configuration to be "Notes Only", check the box against "Is Default Configuration" then map out a pair of properties such that the values of dRofus' "Note" goes in to Revit's "Type Comments" as follows:
The Sub Configuration has now been setup as follows:
The next time you open the Family Type <-> dRofus Item dialog, you will see that there is a "++" symbol next to the active Configuration, indicating that one or more Sub Configurations may be applicable if you were to run a Synchronization:
If you were to then run the "Sync all" command, you will note that (although the Revit Category Filter has been setup to include Families of Casework, Doors and other Categories) dRofus' "Note" values that get pushed in to Revit's "Type Comments" parameter will only apply to Revit Families of the Electrical Equipment Category.
You are able to create as many of these Sub Configurations as you like.
To delete any existing Sub Configuration, simply click on the "-" button next to the Sub Configuration which you would like deleted: