Open a reference to the VI, wire it to an invoke node and select the Reinitialize all to default method, close the VI reference...that's it. You can put it into a sub-VI and have it accept a string with the VI name or the VI path as input.
If there was no such method you could have accessed the properties of all objects by getting a reference to the front panel and from there an array of references to all objects, then you could reset their values in a for loop that was fed that reference array.
