to get separation of materials that touch,
the materials need a different cross section fill,
or Archicad will connect them (think of stacking slabs, no separation lines)
you will need different building materials(with different sectional fills) applied to the elements you want to separate.
if you change the building material(or section fill) of alternating cabinet carcass then you can have lines created.
i don't know if the cabinetry you are using will allow that to apply individual building materials to the components as you desire.
i assume you want the bench top to connect, but the cabinets to be separate.
i don't know if this helps as i do not know which cabinets you are using.
if you change the overall cut section of each second object to a different fill then you get unit separation.
I changed the fill from "Background" to "Air Space" for the middle cabinet.
The object needs setting for sectional fill for individual components, like the surfaces for individual components, or an upgrade to building materials.
i don't know if this helps
I am up to page 4,078 of Archicad 26 Reference Guide, (Worksheet and Detail Tool Settings), but i got to read it all 😞