iGO Primo/Nextgen/Luna is by far the easiest navigation app (that i know of) for on-the-go route editing
sadly it you want easy route building via pc/another app like Gmaps or the fantastic Tomtom MyDrive, this ain't it... can't have the best of everything
sure i guess you can build a complex route in gmaps and export kml files and whatnot... but why bother? 99% of the time i find it easier to just grab the phone/tablet and do it my way...
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