There is not much you can do at the moment.
Camunda Modeler currently does not support vertical pools. However, its next version, which will probably be released in mid-January, should be able to draw vertical pools correctly. However, this does not mean that modeling will work. Modeling may be implemented in the future. You can see how much vertical modeling is implemented by viewing the link you’ve been given.
If you want to try vertical pools right now:
Create a new model in Camunda Modeler, place a pool in it, then switch to the XML view (bottom left) and change the isHorizontal attribute from true to false.
Save that model and open it in bpmn.io
Note that this is no “magic switch”. For instance, this will fail to work in most cases for lanes.
However, if you have created vertical pools and lanes in another tool, bpmn.io is now able to draw (render) that correctly.