If I remember correctly, Shotcut has no such option or is limited. I don’t remember where the author of Shotcut explained it so well. I found some other explanations but not as good.
The keywords to find the solution to your question are
“without export” and “without reencoding” This information is also in the FAQ.
The answer and solution is e.g. the Avidemux program (allows you to use the copy option) to cut out the fragment(s) and save them without exporting. It can also be a mini editor. Cut precision may be limited by keyframes.