In general the following rules apply:
If you're inscribed for multiple smajors at the TU Graz you can only elect the inter-universital representation once.
You may still elect the students council for any major you're inscribed to.
Examples of cojoined studies are electrical & audio engineering or natural science studies such as chemistry.
A study being co-joined dos not guaranteee that the student councils are too.
This means you'll elect your student council twice, both at the TU and then once more at your second academy.
In total you elect two student councils, one at each academy.
As major in education you're registered at the south-eastern bond of all universities. This means you can attend the election at any academy of your choice.