DJI did actually release a SDK for Mini 3 and Mini 3 Pro, as well as Mini 4 Pro, but not Mini 5 Pro (will they ever? who knows).
Of the Mini 3&4, only the Mini 4 Pro can do waypoint using the onboard engine (with option to continue beyond signal loss being available depending on local regs).
For Mini 3/3 Pro, you can plan on Litchi Hub and fly using Litchi Pilot (Android only - [OPEN BETA] Litchi Pilot)
For Mini 4 Pro, you can plan with Litchi Hub and fly using either Litchi Pilot (Android only) or DJI Fly (both support onboard waypoint)