It can be loaded dynamically, you don't need to have it in the project.
One thing that does need to exist beforehand, is the 3D geometry representing those tiles and their link to particular map tiles.
So your .tsx will have to be done beforehand, unless you really want to do a lot of work to handle that dynamically (I do not recommend this).
.Tmx is all good, though. They can be changed at will, and can sit in any directory on the cpu as long as your app knows the path. OBEY works like this.
Last edited by dez
on Thu Jan 10, 2019 2:21 am, edited 2 times in total.