Hello John,
Yes there is a scheduling option in the native portal. It is limited but it is there. You can experiment with it in the demo.
There is not a scheduling option in the wordpress option. What I have been using is Easy!Appointments and I have heavily modified it for healthcare in the US. My last version is posted here: GitHub - CraigT543/EasyBlue: Modifications for Easy!Appointments
I have clients schedule on Easy!Appointments and then when they show I enter the appointment into OpenEMR. That is not the most graceful method. What I need to do is to modify the webserve.php in the Sunset Patient Portal plugin to handle the scheduling stuff on sync with OpenEMR. But this is working for me now.