Well, from that screen capture, it appears that the ToCall is actually required entry by the user on the PAth command.  I'm suspecting that the TARGET is the ToCall and then the actual path is composed of the DIGI0 .. DIGI8, even though that range would imply 9 supported Digis, the actual AX.25 packets only support 8 as the description states.

So, if the user has to specify the TARGET and that is indeed the ToCall, it's highly unlikely that any official ToCall would ever make it into most of the deployed TNCs.  If you have a line to the firmware developer, I'd lover to interact directly with him/her rather than relaying through you, who appear to be just an alpha or beta tester?

For an official ToCall to be effective, it should not be something the user has to specify along with something that would ordinarily be user configured like the path.  If a dedicated, defaulted, ToCall (destintaion call or TARGET) is a configuration parameter, then it will be more likely to be kept at the official value rather than at risk for misspelled entry in a PATH specification.