I understand that you have created a 2*1 tiled and are trying to superimpose another axis on the second tile.
By manually creating an 'axes' object with the tiled layout chart 't' as the parent container, the axes goes to the first tile by default.
In the code you have provided, inorder to create a new 'axes' object at the second tile, you can first create the axes 'ax4' with 't' as the parent container, and then manually specify the tile location by changing the property 'Tile' , inside the 'Layout' property of object 'ax4'. This can be done by adding the following lines of code:
You can refer to the following Documentation to get a better idea on it :