user expectation – How to design schedule service interface

I suppose is a big question.

I am trying to create understandable and clear UX design for schedule designer web app. May be, In a fact i’m looking for some well-known practice or production-ready interface, which fits our goals too.

So I think I have to describe our web app entities. To make it easier to understand my question I change names some of them to more usial.

So, imagine we have categories of followers and marketing emails to send. Also we have a schedule: each day we are going to send some pool of emails of some category.

Here is data model:
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Also, I have to notice, that sometimes, we need to move some email of some category to another day of schedule, so
emails of day ≠ emails of followers category, even that looks like it.

What I decide to design right now:
enter image description here

The main key of this screen is Generate schedule button. We suggest that user needs to arrange categories to days and generate schedule from this screen. If user needs to move some email to another day so user could do it on another screen, when viewing generated content, and this idea looks bad.

I feel like I’m trying to reinvent the wheel. What is the most right pattern in this case? What already existed decision could fit my goals? Where to find right inspiration to get this done?
Any ideas or questions are welcome…

UPD.
The most problem is that user need to pre-generate schedule, and move some emails to another day if needed. But what if user wants to change schedule and generate one again? All corrections of previous version going to be lost. I look for decision where user could create “ready to use” schedule on fly.