Manual bed levelling 4 motors

Printer: 7h7 reprinter, two hiwins on sides and 4 motors in corners
Mainboard: MKS SBASE 1.3 latest firmware

Question: Bed level difference between front and back is over 5mm. 7h7 claims it is adjustable via that 4 motors in corners. How to do it? There is no bed levelling in Prepare menu.

Since three points determine a plane, it seems weird to me to have four motors for Z. But… The Voron 2 uses four motors and has firmware that supports it, so maybe that helps…

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One side pictured.

I could do it manually by rotating motor screws. Need advice which extruder choose for 3mm filament and 1mm nozzle? Possibly water cooled. PLA wraps like crazy. Glass bed.