The option MPConstraints does not work in Navigator. The values you input in the window are not taken by OSNavigator, they are not plotted on the screen and they are not written to the Tcl file.
I am using release 2.5.7 (build 541). MPConstraints works only with release 2.5.1 and earlier releases.
I can not reproduce this issue. In version 2.5.7 (Build 550) the MP-constraints seem to work fine, when I create a new model.
Are you opening an old model created in version 2.5.1? If so, please try running the ‘File -> Update OSN Model…’ command to see if that resolves the problem with the MP-constraints