So basically you only want to show certain regions of your Map and be able to change the ones shown while playing the game, correct?
While you can not hide certain tiles you can set a specific tile using the method
set_cell( int x, int y, int tile) (or alternatively set it using a Vector2 by calling
set_cellv( Vector2 pos, int tile)). The first to parameters are the grid coordinates of said tile and the third one describes the index of the tile you want to use. Set this to -1 if you want to clear the cell.
You could create an array with a bunch of dictionaries at runtime which each hold the position and tile index of a tile. You can later iterate through this array and set all of the contained cells once you need them again.
Did that help you in any way? If you need clarification about anything, I would be happy to further explain :)