On spec editor, is there any way to change "Default Flange Type" to "Flange Lap Joint"? The only possibilities are SW, THRD, Long Weld Neck, Weld Neck and Splip On.

https://prnt.sc/oiezcq

Nope, I've asked for it to be added but its been a while since then. Submit a SR to further escalate.

Ok. Thanks

If you set it to Show Options, you will get Stub listed. From the Speceditor you can assign a default backing ring to the stub flange to have the lapjoint placed automatically.

Its not exactly what you want, but this is closest you can get.

Thank you for the help Vanman, but don't understand exaclty what you're proposing. Can you please be more detailed?

If I am understanding your question correctly you could do the following with the piperule set to Show Options for flanges.

When I try this I get two backing flanges automatically placed. Is there a switch somewhere I need to turn off?

Are you able to share copy of your spec ? I have only seen this behavior when custom end types are assigned to the stub flanges.