With the initialopendirections option, you can open the directions and specify the “to” location as a number (0 is the first POI, 1 is the second, etc.):
If you want *both* locations filled in it’s trickier:
1) Modify the directions.php template and enter the default addresses in the input form, then use initialopendirections=”true” to open the directions when the map is displayed. This will still require the user to click the ‘get directions’ button and it’ll always use the same 2 locations.
// Open directions between two addresses:
mapp0.openDirections("first address", "second address");
// Open directions between two pois:
// Click the 'directions' button to get the route:
Note: each map has a name – “mapp0” is the default for the first map on the page. You can override the name using the “name” option in the shortcode: