How to Delete Old Routes in Basecamp Lists

If those points are individual waypoints then deleting routes that contain them won't delete the waypoints 

Thanks for the reply, when you say 'individual' waypoints, do you mean Waypoints originally created outside of any route? I have the start and destination Waypoints for every original created (not duplicated) route in my All Data List.

Thanks you were correct. I did a backup first but after route deletion I still have my WayPoints created out side the Routes.

I surmise what the Basecamp message was referring to are any interior via points created upon the software's route creation, or by User by editing or adding to the route.
Or also if the route was created by Duplication, then probably all it's pts would be deleted with the route(?).

Waypoints, Routes and Tracks only reside in My Collection.  Lists refer to these objects within My Collection like making a list of things in the real world.  For example, you might make a lists for a camping trip and a trip to the beach.  For both trips, you want to take your cooler.  So, you write cooler on both lists and it refers to same real object, it is not the object itself.  This allows you to cross reference an object in different lists/folders.  Think of an old fashioned card catalog.  A book in the library's collection resides on a shelf, but it will be referenced in the catalog by Title, Author and Subject.  

BaseCamp uses the name of an object as a unique identifier.  Two Waypoints can't have the same name.  A Waypoint and a Route can have the same name because they are different objects.

When you copy an item on a list and paste it to a new list you are creating a reference to the same object in My Collection.  Your are not creating a new object.

Routes need a start point an end point and can have via points (places you want to reach) and shaping points (points to direct the route as you intend).  Waypoints can be used for any of these points.

When you duplicate an object you are creating new object whether it be a Waypoint a Route or a Track.  BaseCamp will give the duplicate a new name by appending a number to the original name.

For Routes that contain Waypoints you have the option to use the same Waypoints or create new Waypoints at the same location with a new name (old name appended with a number).

For points in routes that are not Waypoints, BaseCamp will create a new point with a new name by appending a number to the old name.

Since lists contain references to Routes, Tracks and Waypoints in My Collection, you have the option to remove the reference from the list or delete the object from My Collection.  Removal only occurs within that list - the object remains in My Collection and any also any lists that reference that same object.  Deleting the object from My Collection requires that all references to that object is removed from all lists.

When you remove a Waypoint that is in a Route from a list, the Waypoint still exists and it will remain a Waypoint in the Route.

If you delete a Waypoint that is in a route, BaseCamp will change it to a point type that is created by clicking on the map and it will be given a unique name in every unique route that contained that Waypoint by appending a different number to the Waypoint name for each occurence.