Extending polylines via basemap reference in ArcGIS Desktop?

Question

I have a polyline feature of a pre-existing bus route (let's call it "Route A"). I want to extend the polyline of Route A, using a basemap as reference. I don't want to totally freehand it, my first preference is for an at least semi-programmatic method (the existing polyline features are sourced from GIS shapefiles). Maybe a picture would make more sense:

Now, if that's not possible in ArcGIS Desktop 10.5, as an alternative, consider Route A and the polyline of another certain route (let's call it "Route B"). How would I be able to snip Route A at a certain intersection, snip Route B at this same intersection, then merge the northern part of Route A with the southern part of Route B?

If you're confused, here's a picture:

I tried rasterizing the features, but that splits them into hundreds of constituent polylines, whereas I want each feature to stay as one contiguous polyline.

Answer 1

To do this I think you should look at Reshaping a line:

The Reshape Feature tool lets you reshape a line by constructing a sketch over a selected feature. The feature takes the shape of the sketch from the first place the sketch intersects the feature to the last.

When you reshape a line, the line takes the shape of the sketch you draw.

You would use the basemap to guide you as to where new vertices should be placed.