Is it possible to show collapsed content in the detailed view and that a button appears that when pressing that content expands and is visible?
Welcome to AppSheet!
No, there isn’t such a feature in AppSheet at the moment. You can approximate it. AppSheet has Show type columns and you can set them to Section Headers. If you show/hide these sections, it will show/hide all the columns within that section.
To simulate expand/collapse, you could add a Yes/No Column to control the Showing and Hiding of the section. Not ideal from a UI design perspective but will get the job done.