Fixing Bed Skew
While bed leveling procedure can build a height map of your steel plate and compensate for it's unevenness, the whole bed assembly or your ZX-gantry might be skewed, which will show as gradient of values on a height map.
Sometimes the skew might be so huge that measured height map of your bed will exceed reasonable values and the bed leveling will fail completely, leaving you with a printer in a broken state.
The basic idea is to use two identical objects of at least 6cm high to check if the left side of the X-axis beam is at the same height as the right one, then loosening one of the Z-rod syncing pulley screws, aligning the gantry and tightening pulley screws back. See the official Creality video for details:
This is sometimes recommended on the community, but quite questionable solution. Remove the steel sheet plate and observe the 4 screw heads in coutouts of magnetic layer. Adjust quarter turn at a time, turn clockwise to lower the overall corner of the bed, counter-clockwise to raise.
Mind that if the bed frame plane would've been mounted on 3 screws, raising one side inevitably lowers the opposite and vice versa, but since our bed is mounted on 4 screws, changing tightening or loosening one screw and keeping the opposite one will create heated plate tension.
Sometimes it's recommended to use shims of thin PLA under the lower parts of your bed to compensate for unevenness. This might be quite finicky, as you'll often be removing the steel sheet plate and that probably would shift shims elsewhere.
Your heated bed plate is held above the bed frame with plastic spacers — two longer on the right and two shorter on the left. These can be replaced with a 2+2 set of silicon spacers, which should further reduce any bed skew.