You must always have a surgeon selected within the platform. In fact, at no point will you ever not have a surgeon selected. This is why we ask you to add your first surgeon before you can do anything else on the platform. Everything you do on the platform (ie creating cases or adding/editing procedures) affects only the surgeon you have selected. For instance, if you have surgeon A selected and add a case for tomorrow and then switch to surgeon B, you will no longer see that case you created because it is associated with surgeon A and not surgeon B.
This is also great when covering a surgeon for a colleague. When you select that surgeon, you will now see all the procedures and cases that your colleague has previously input. Making your workflow much easier.