Load a Std. Base Frameless with Toekick into the cabinet editor.
Click one of the end panels to highlight it, and take it to the Part Editor.
Select the Rectangle tool, and use it to cut a notch on the opposite edge of the existing toekick notch (such as you would do to make a cabinet with a toekick on both sides).
Return to Cabinet Editor, then go to Constraint Editor.
Constrain the cut vertically, and set the dimension to 5" (the same height as the existing toekick).
Click the Main button to return to Cabinet Editor, click Yes to apply dimensions and constraints.
An error is presented: "Can not add all the constraints to the part. This part has been over constrainted". (my inner grammar nazi is yelling at me that "constrainted" isn't a word...lol)
Not sure if this is a bug of sorts, but any other dimension other than the height of the toekick will work.
I see the same thing, I reported to software engineers. If you are desperate to make it work, looks as though as long as you don't set it to the exact toe kick height it works. Example, 5" on a 5" toe kick will error, 5.001" for the constraint on a 5" toe kick will work.