There is not currently a creative mode development roadmap trello, however the developers have discussed their general plans for creative mode in the past. Creative mode is currently in active development, with new features and improvements being worked on regularly.
The developers have said that they want to focus on making creative mode more flexible and customizable, with more options for terrain generation and object placement. They also want to make sure that the mode is well-suited for both singleplayer and multiplayer, and that it supports large-scale creations.
Unfortunately, there is no timeline for when these features will be implemented, as the developers are currently working on other areas of the game. However, they are regularly providing updates on their progress, so be sure to check back often for the latest news on creative mode!