Q:

Is there a way to keep treasure locations on the map in New Game+?

When you find treasure in the field the location gets marked on your map so that you can easily find it later. Is there anything that allows you to bring these markers over into New Game+? 

A:

No. There is no way to transfer these markers across games. 
You only need to find 800 unique random treasures (sparkles and white bags) in order to all associated titles in both games. Random Treasures in areas you only have access to once are not included in this count as mentioned in this question.

