Hi @Lukas Steffensen,
Thank you for posting in this community.
Per my knowledge, we can use Refinement web part to add the terms as a filter. Did you set it up this way?
If not, please tell me how you implemented the use of terminology as a filter. I will test it the way you did.
If I'm okay with that, I'm sorry, we can't collapse the terms. Because Refinement web part is a refiner that helps users quickly narrow down search results. Folding it up is not conducive for users to quickly find what they want at a glance.
This is the way SharePoint is designed and there is no way for us to change it at the moment.
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