This window lets you create a gap between structured Parts automatically. This option does not work for unstructured parts and therefore unstructured Parts will not appear in the window.
Gaps are created by reducing the size of surface elements of the selected Parts, so there will be small changes in the mass of the Parts that are modified.
You may prefer to manually inset gaps using the Translate and / or Scale options in the Zoning panel (no mass will be lost).
The box in this window lists all Parts involved in interactions.
Select the Part(s) you want to adjust while creating the gaps and click for Autodyn to automatically create the gaps.