Can't organize linked DBs structure

Hi, guys. Need your help.

I am working on an appointment app.
I have 2 databases and their structures are described below:

My use case is that user enters his name, phone, start date, end date & event name(purpose of appointment) and after he books it, I want Client’s name input’s value go both to ‘Calendar events’ DB & ‘Clients’ DB. I can’t set ‘Content format’ as ‘Clients’ in the editor:

Additionally, I can’t make to actions in workflow (sending data to both DBs). I can only send the data to a single DB:

Need your help, guys. Is there a workaround to my problem?

Just add a second 'Create a new thing"

What should I do if I want to “Make changes” in “Customers” DB’s field, but in my editor I am working with “Calendar events” DB. So, I have a column in “Calendar Events” that must connect “Calendar events” & “Customers”. For example, When I create new “Create Field”, I want to create new “Customers”, but if there is Phone number that already exists in “Customers”, then I only want to find row in “Customers” with that phone number and add +1 new “Event name” (it is a list).