Is there a way to edit my personal maps within Google Maps or any other application?
Unfortunately I couldn't find My Google Maps Editor either.  I can't read Google's future and couldn't find any indication of such a feature but Google's My Tracks does allow you to upload a map to your maps but I'm pretty sure you'll actually have to run/walk/bike/move-in-some-way over the course you want to map.  

I also did a Google search for "my maps editor apk" and looks like you can still find the apk somewhere (I'll leave that to the you) but I can't say if it will work or not and you should always be careful downloading apps from unofficial sources.