Proposal to allow creating a field and setting its value in one go

I always find it very tedious to first enter a field name, click "add" (could you add "Return" here as a shortcut?) and then to click the newly created field to enter the value. Especially when an instruction shows field and value like this: "field: value".

This proposal splits a field name at the first colon and sets the name to be the left and the new value to be the right part.
Why split more than necessary when you join almost all of it later?