I was able to dock a vessel with itself in KSP 1. Example of use was with wide vessel, in the centre is 1 large fuel tank with say x8 symmetrical fuel tanks pointing down attached to it's side. I wanted to save the launching vessel (for financial reasons) so I didn't make x9 separate launchers as all of them but the one I was controlling would be lost in orbit as it descended down from it's sub orbital position. I instead had 1 large fuel tank with other fuel tanks connected symmetrically to it's side, just like the payload it was delivering had. As you know, you can't do multi decoupling. so Instead I only had the centre large tank attached to the payloads large tank by a decoupler. All the other fuel tanks had docks on them but the docks had not been attached to each other in the VAB and instead they were attached to the fuel tanks which were positioned so that the docks were next to each other, like they would be when docked. When I launched the vessel, they all docked and showed in the information window as docked. I also "enabled staging" on the docking port in the VAB and put it in the same stage as the main decoupler in the centre and when I activated that stage, they all undocked with the decoupler (on most occasions), sometimes I would have to manually undock them. I have also used docks before as locking mechanisms for attached rovers and this worked in a similar way.