It looks like entering each date separately is currently a requirement for the Scheduler appointment group. Your suggestion works well as an idea to improve Canvas, so I suggest using the idea process. If you decide to do this, make sure you mention that Canvas already has a process for creating repeating calendar events. The Instructure developers can probably reuse that logic to implement your suggestion.
Creating an idea does not provide an immediate solution to the problem you described, though it is a solution. I’m going to mark it as such and hope that our colleagues who have a similar challenge will find the best way to contribute. If you decide to create an idea, please link it here so mode community members can support it.