Unfortunately there is no way currently to mass delete an item in surveyor which you no longer want on your layout. You can only mass replace using the “Replace Assets” function. This very small low poly (24 triangles) invisible marker can be used in conjunction with the “Replace Assets” function in Surveyor mode to mass replace something you no longer want on your layout but can't seem to get rid of because there are too many of them to just manually delete one at a time. This method will work with any content item shown in the Objects Tab (Object mode only) in Surveyor. This method will not work with splines.