I don't believe that this option is available. I know that I had requested this less than a year ago but was told it was not offered. My husband wanted the soft close so that is how we went. In a way, it is prob for the best in case we decide to ever change the doors or want to update the look years from now.

It is done on some higher end brands, rare earth magnets are mounted in the top and bottom of the door with magnets also inserted in the rails, then a soft close piston can be used. Note that the brand I'm familiar with (QCCI) also uses a mortise hinge. They need to be made that way from the start, would be a nightmare to retrofit.

Could you not purchase and install a soft close damper (on the inside) using regular/your favorite exposed hinges?

for inset cabinet doors with a butt hinge, I found these soft-close and magnetic catch -- all-in-one things.

Here is a link that might be useful: soft close mag catch

I have (new) full overlay doors on old cabinet boxes. The hinges are not soft-close, so I bought Blum adapters and added them myself. Works great. Soft close!!! Best and easiest DIY ever.

Obviously the adapter is attached to the frame into which inset doors would nestle, so you can't put it there. But couldn't you put a dummy piece of wood behind the inset frame and attach an adapter there? It would allow the door to close quietly and flush, and the "tongue" would only stick out when the door is opened.

You could work out getting one in there, there are even other options that would be easier to place. Problem is that the standard catches used on insets are not strong enough to overcome the soft close feature.

Could do the soft close with a dummy/"just for looks" exposed hinge