Nothing about using multiple adaptors to connect 50/30/15 inside a storage area, is dangerous .
Now being outside in an RV site in the rain connecting the 50 amp cable to the site power post without turning the circuit breaker off ; well that's a different story.
If your charging system is part of the inverter function , then you'll need to leave the " Inverter circuit breaker on. Wait 3/5 mins after connecting and use your multi meter to check supply volts to both battery banks.
If the power supply is a GFCI outlet , you may have issues with the GFCI tripping . There are many threads about the issue .