By default, OLab4 and OpenLabyrinth start each map at the root node. But sometimes, you want to start from somewhere else in the case or map. For example, in one of our cases, we included a bunch of small sub-cases. In OLab4, you can simply change the URL to point to the new starting node, but some changes in our security model will now sometimes prevent this.
The easiest use case is when the map has been marked as openly accessible to users, whether they are logged in or not (anonymous play). In this situation, you simply append the node number to the URL path e.g. https://logan.cardinalcreek.ca/player/5/4815 will take you directly to a page within the Welcome map.
Note that OLab4 now has more controls over who can access which maps and we also have Role-Based Node Access, Role-Based Node Access in OLab4, where authors can limit which user roles can read which nodes in a map (a powerful new function, but a wee bit fiddly to set up.)