Shotcut doesn’t have markers yet. There’s no easy way to do what you want to do.
You can create markers. Put the audio on an audio track. Zoom so you can see the waveform and the beats. Put a color clip equal to the length of the song on a video track. I usually put it on V5.
Cut the color clip at the beat using S to split. You can do it visually, or if you know the music well, just let the song play and hit S at every beat. Put your images or video on a lower track. Use the cuts on the color clip as markers.
It’s not easy but it’s doable.
Made this before the ADV filter was added to Shotcut.