Hey @xor0110,
this has been a long term issue, but with Julia 1.3 and its threading capabilities it actually works. Have a look at this example.
The point is to spawn the thread and put all UI code into an idle_add.
One missing piece in that code is to spawn the thread at a different thread than the master thread. There is some package exactly for that purpose, but I have not tried it yet (you need to search in the forum, I do not remember the name).