Why isn't there a "minimize" option for a line trace hit result?

Don’t think so. I’m going to tag your question as Feature Request.

This is possible when breaking a user made structure but not a hit result structure.

The giant hit result structure:

The minimize button for my own structure (the upwards triangle on the bottom of the break):

I second this! Every type of break item should be collapsible to only show the currently used outputs. Especially the Break Hit one is huge.