how to set blocks in custom map stored as file document #914

if we generate a maze using MazeDecorator，we can easily set Waypoints blocks which can be indicators or rewards for the agents.

now we have some custom maps stored as file document, after loaded them into the malmo, how to set blocks on them especially on the potential way like Waypoints in maze?

we explore the source codes of malmo (in C++) , but found nothing about implementation of Waypoints Decoration.