I have to disappoint you. The Learning Interactions (I think you mean those, don't use the original widgets because they are not compatible with HTML output) are 'closed'. There is no way to force anything like you want (don't agree with that forced behavior at all, but that is off topic). The acoordion interaction is a static interaction, there are no variables nor events linked with them.
If you need to 'force' you should have to create a custom accordion, which is possible with a multistate object.
About forcing views outside of the learning interactions:
In this post you'll find a descriptive table of the interactions, and explanation of the difference between a static and an interactive interaction:
As for buttons a tip: shape buttons (smart shapes with Button functionality) are the only interactive objects which can be on master slides, timed for the rest of the project and can also be used on question slides. None of the other interactive objects have that functionality.
Thanks for the bad news
Seriously, thanks for the quick response. I'll check into your suggestion about States (first time for that too I guess).
BTW: what are smart shapes? Is that different than the Shapes dropdown?
Yes, the official term is Smart Shapes. When converted to button some label it still smart shape button but I call it a shape button. Have a look at this old post:
You can also have a look at this recent post, written for CP2017 but works also in CP9, could be an alternative for your accordion. You can add audio to states without problem. A state can have text and images.