Marlin offers a bunch of different choices for auto-levelling and assisted manual levelling for bent build plates (mesh levelling), but for the moment I want to level things completely manually.
That is, I want to move Z to 0, disable steppers, and then move around the print head and adjust the distance between bed and nozzle at various points with a piece of paper.
With the old Repetier based firmware on my printer, selecting "home all axes" did not only home XYZ to endstops, but it also moved the head to position (0, 0, 0) afterwards. Then I could simply disable steppers via the menu and go on with my levelling. Note that in my case, the coordinates of the endstop positions are negative for all axes, so moving to the endstops alone isn't cutting it.
With Marlin, selecting the "auto home" option merely moves to the endstops and then to some positive Z position (+10). This means I have to use the menu to manually move Z back to 0, which is quite inconvenient, unless I have a PC nearby that allows me to enter G-code.
So, that leaves two related questions for me:
Is there some simple way to move to (0, 0, 0) with the menu?
Can I implement an assisted manual levelling (i.e. some procedure that simply moves the head between a number of different X/Y positions) easily? Does something like that already exist? If not, I wonder why.
Write a few pieces of gcode to do this. Place it on an SD-card (I assume you have a reader) and select the file you want to execute.
G28 G1 Z0
Do you really want to home it directly? I would say you want to take it down slowly and adjusting end-stops incrementally.
G28 G1 Z10
G28 G1 Z3
G28 G1 Z1
You can also move it around in the X and Y plane:
G28 G1 Z5 X50 Y30