The benefit of blowing that whole shit up ASAP far exceeds the benefit of not killing the hypothetical forced labor on board.

Slaves and conscripted labor were used in its construction, but by the time it was "fully operational" the slaves would've been shipped out and replaced with the elite of the imperial military hierarchy, everyone of the million or so personnel would have been picked from the top names of countless lists, the Death Star was the most prestigious posting in the empire and there's no way slaves would be present in any significant numbers on such a mission-critical piece of tech

The battle station housed 342,953 members of the Imperial Army and Navy, 25,984 stormtroopers, and nearly 2 million personnel of varying combat eligibility. Furthermore, although there were communal barracks, there also were enough private bunks that most people could expect to receive one within three to six months after arrival. While enlisted personnel used walkways or turbolifts that could move both vertically and horizontally, officers had access to a high-speed, officer-only shuttle system that orbited the station. Massive housing blocks for enlisted personnel featured a large atrium for off-duty personnel to walk in. Officers could expect their own exclusive accommodations. Life-support modules inhabited by workers during the original construction of the Death Star could still be used in an emergency. The station featured several hospital wings. Several color-coded life-support modules existed in the station's lower levels: gray for workers, red for overseers.

Meant to function as a world of its own, the Death Star had creature comforts most other Imperial Military postings did not: decent food, recreation areas, cantinas with latest-model bartender droids, and commissaries with selections of expensive treats and luxuries. The Death Star had its own commissary and bar. Off-duty stormtroopers were known to clandestinely meet to play violent, prohibited ball games in the station's zero-gravity filtration system.

The station's detention block, while large and formidable, was not intended to hold prisoners for extended periods of time. Instead, it served as a place for temporary detention and interrogation, pending transfer to planetary prisons, and execution. Prisoners were kept on the Detention Level in complete darkness, then moved to bright interrogation rooms

The part in Andor where they're in prison, those things they're assembling are structural struts for the Death Star.

That was an interesting twist in Andor

That's a good point, though I wonder if they would have taken the risk of having slaves working onsite on such an important piece of equipment. Still, probably best to storm the place and capture everyone for trial. We can always blow the empty station and put it on the Holonet later