Hi,

This option is available after setting up an external zone.

3 things to consider

-the first is the inner option or the outer option which will affect the overall dimension

-Secondly, it will block the possibility of using a filler as a plinth under several cabinets in project mode

-and 3rd the plinth always follows the dimensions of the bottom by default, which can overflow with a groove or mortise to the sides

Hope that’s helpful, 

All the best, Alex