Superb answer, stunning! so you say you should be almost sure you avoid yaw error this way, but how to be fully sure? If the craft wont show any compass error or any error, can It still be having one compass error? thanks a lot.Yeah ... that's good, but a yaw error isn't created at "take-off".
When you power on your drone the IMU know nothing about the cardinal directions & how the craft is pointing in relation to those ... and it's the IMU that's primarily used airborne, not the compass.
A yaw error is created in the moment when you power on your craft ... in that moment the compass will tell the IMU the cardinal directions. If the compass is deflected in that moment the IMU will be wrongly initialized & cause it to believe that the craft is pointing in another direction than the correct one. The compass will quickly be corrected once leaving the disturbed area ... but the IMU will remain wrong.
So if you accidentally power on your craft too near magnetic interference ... & then put it down for take off far away from magnetic objects the damage is already done.
Then regarding landings ... or general flying near or in a magnetic disturbed area. It's correct that the compass will slooowly feed in corrections to the IMU over time, so leaving the craft in magnetic disturbance will eventually cause problems but it will take time, both due to that you rarely are that near magnetic objects during flight (like a drone foot/leg distance from it) & due to that the compass isn't the only one that feed in corrections to the IMU, both the gyro & the VIO sensor (a turning measurement created from the bottom VPS sensor) does that also. I wouldn't be particular afraid of magnetic disturbance induced problems neither during flight or during normal landings.
Power on your craft in your out stretched hand (no watches, bracelets or rings near that hand) ... then your craft is around 1,5m above ground & away from your body/clothes with perhaps zippers & buckles. Once the live view have been activated in the app the IMU have been properly initialized. After that you can place it on ground for take off. Before getting airborne you ALWAYS check the drone icon on the map in the app & confirm that it's pointing equal to the map objects (roads, houses etc.) as the craft does in reality.
Do this & you have massively minimized the risk for a yaw error ...