When a time signature change occurs at a system break, either in the score or in a part, the new time signature is shown at the end of the first system as well as at the start of the new system.
This is sometimes considered a “cautionary time signature”, because it warns performers of an upcoming change of time signature before it takes effect. It is also known as a “courtesy time signature”.
In Dorico Pro, the time signatures shown at the end of one system and at the start of the next system are the same item, not separate items. You can hide cautionary time signatures, either individually or by default in each flow.
We recommend using flows for separate spans of music. Dorico Pro does not show cautionary key signatures or time signatures between flows.