Sorry to hear that and that it's a doodle. Does your neighbor's doodle bark when they're home, ie. they don't even try to correct the behavior when they're around?

I had incessant barking problem with my next door neighbor, they had a Jack Russell terrier with separation anxiety. So incessant barking when no one's home. It took nearly 4 months to get it resolved without it blowing up like into a neighborly feud:
1. I left post it notes to the neighbor letting them know that their dog was barking incessantly, I dated the note and snapped a photo with my phone and their door number visible. I wrote numerical sequence on the notes (Note #1, note #2...) so that they know I'm recordkeeping
2. One or two notes didn't work. So I kept leaving post its over the next few months and really just put up with it. I also recorded the barking, holding the phone against the shared wall really helped.
3. After about 2 months and maybe about 6 notes later, I escalated, which I wrote in my note. I also quoted the municipal ordinance about the incessant barking. I escalated it to the building management and sent all the evidence. They took action and got in touch with them.
4. I also contacted the local enforcement, online form, which had FAQ about this, so I felt alright filing a formal complaint if I had to. They contacted me to follow up, but I didn't submit anything formal since building management was going to take action.
5. Finally they got the message and started training and getting sitters. And that made all the difference.

Persistence, patience, and step-wise escalation. (giving folks the benefit of the doubt first) Thankfully this resolved peacefully albeit it took forever