Hello Author,
I don't exactly understand what are you trying to do from description or from the screenshot, but here are two short-cuts:
- In general, transparent object should be displayed on top of opaque objects.
This might be achieved by handling priorities and Z-Layers in OCCT.
- Order-independent transparency is currently available only within Ray-Tracing output in OCCT. You might refer to the following feature request on a bug tracker #27716.