Hi David,
Thanks for the note.
We currently do not provide the capability to merge flights, with that said we will pass your feedback along to the product team to see what could be implemented in a future release.
Also, while it is not a full merge functionality, you can group flights and see the flight paths in the overview page of the group.
To create a group:
Select the flights to group
Click "Actions" at the top of the flight list
Click "Group/Ungroup flights", then select "create new group", enter the name of your group in Title then click on Save.
Hope this helps,
Frederic