I was wondering that exact same thing until I came across a product called ProBond Max. It works great and is readily available here in the Canadian marketplace. I picked up my bottle at my local Home Hardware store.
Gluing thermally modified wood can pose some issues. I found that the processing time needed for the glue to be absorbed into the thermally modified wood resulted in a longer cure time because the thermally modified wood has a lower moisture absorption resulting in a slower penetration rate. It does say to clamp your glue line for 1 hour but I did not follow this recommendation as I wanted to see how strong the bond held without clamping and as it was I did not need to clamp as the strength of the bond was outstanding.
I decided to use the ProBond on a recommendation of a contractor friend of mine who provided me with some thermally modified wood to build a small picture frame. After the glue had dried (24 hours) I sanded the glue line with a medium git sand paper. I did not use any screws or nails on my project as I was looking for a very clean look n the exterior of the frame and the performance of the glue allowed me to achieve this.
The thermally modified wood was easy to work with. I used a species called North American Ash. Cutting the wood was easy but I had to be careful around the edges of the frame when as the wood seemed very brittle and if not careful you would get tear out. The wood was a consisted chocolate brown color similar to Walnut but without the knots. My pieces of wood were nearly all clear and free from knots.
Elmer’s ProBond Max works well on thermally modified wood.