@Jetson-Nano If using QGC for mission planning, indoor missions are more of an approximation since openstreetmap displays no indoor spaces (e.g. approximating waypoints on the roofline of buildings). If there's a way to overlay an indoor floorplan/raster or add custom maps using a WMS server into QGC would be ideal. Then you can ingest a floor plan of a indoor space and perform precise waypoint planning. Note QGC mission planning provides distance info between waypoints, so one can construct an fairly accurate flight pattern (e.g. for navigating known aisleway & starting point for example).
To describe what's happening under the hood: we're using QGC's takeoff mission item as the local position origin for VIO, and its registered lat-lon is used as a global position offset (though you can manually type it in as well in QGC). From there, waypoints are executed in reference to that origin and true north (of the map). In the end, you're basically flying a pattern based on the take off point and true north. Hence, it doesn't matter where you fly on the map cause this feature is telling PX4 where the drone is located in global space (when running vio only)--and executes the same flight pattern [on the map] from the distances & heading.
Alternatives for indoor "mission planning": we do offer voxl-mapper (trajectory-style) as well as wps mode in voxl-vision-hub (waypoint-style), though both are offboard mode planners in local space and thus precise by setup, but being offboard-mode based, you do not get all the safety measures that PX4 mission mode provides (e.g. RTH, PL, Geofencing, Auto-mode, etc...).