Oh I see. Hmm, there is no straightforward way to do this that I can think of. However if you really want, you could try this method:
(1) IDPrim #1
(2) IDPrim #2
(3) ExpandOrShrinkObjects > Shrink #1 by one pixel (This is a hack to keep touching objects separate)
(4) ExpandOrShrinkObjects > Shrink #2 by one pixel
(5) ConvertObjectsToImage > Binary #1
(6) ConvertObjectsToImage > Binary #2
(7) ImageMath > Add. Add the two new binary images
(8) IDPrimary on the new added binary image with a manual threshold of 0.5. This is your new object class.
You could re-expand your new object class when you are done if necessary, to compensate for the shrinking done earlier.
Hope that helps!