The best way to do it is to go to Cover > Flashings and use the [Single Line] command.
✅ Steps
Go to Cover > Flashings and select [Single Line].
This will bring up the Flashing List dialog.
Select [Single Line].
Select [Add Flashing] to add the additional flashing (or multiple flashings) to that line.
Notice that you have an option to:
keep the existing definition for that line type, or
ignore the current definition and simply quantify the new item(s).
All previously defined accessories for each and every item are automatically quanified for each new flashing item added.
Select [OK].
The software will ask you to locate any other lines that are of the same configuration. Once you have selected all the lines on the model then right click and select [Yes] to however many line entities you have changed.
When you select [Generate] to generate the flashings, you will get the cut list that includes all of the additional single line flashings and their associated parts.