Absorb

Press shift+a to run jj absorb on the highlighted revision. Absorb automatically moves changes into the most recent ancestor revision that touched each changed line.

While absorb runs, revisions that will receive absorbed changes are annotated with a hint inline — giving you a visual cue of where each change is going before the operation completes.

From details

In the Details view, select specific files with m or space and press shift+a to absorb only those files.