DJI hasn't made consumer drones with user-selectable Atti Mode for many years.
Atti Mode is what you have when your drone doesn't have GPS reception (and is unable to use the downward-facing sensors to maintain horizontal position).
Atti Mode =...
On a Mini4P Atti is only a mode that it goes into when GPS signal doesn't meet minimum requirements - AFAIK it is not manually selectable using the regular controller / software.
However that should not cause you great problems flying indoors IF...
It's been a long time due to me not driving, but here's a new drone video I shot today of the beautiful Galeon Andalucia, a replica Spanish galleon, leaving Penzance Harbour this morning. A shame it was such a grey & misty morning.