Refer to Manta-E3EZ/Firmware/Klipper/generic-bigtreetech-manta-e3ez.cfg at master · bigtreetech/Manta-E3EZ · GitHub for a general config of this board and its corresponding pins here Manta-E3EZ/Hardware/BIGTREETECH Manta E3EZ V1.0-PIN.png at master · bigtreetech/Manta-E3EZ · GitHub.
This board has 5 driver slots and you can assign them as you like. For example:
[stepper_x]
step_pin: PA14
dir_pin: !PA10
enable_pin: !PA13
... # rest of the settings
[tmc2209 stepper_x]
uart_pin: PB8
The uart_pin: PB8 tells you that it is the first driver slot, commonly used for the X axis and the [stepper_x] section tells Klipper that you expect it to be your X-axis.
If you rather would like to connect your extruder to the first driver slot, you could do:
[extruder]
step_pin: PA14
dir_pin: !PA10
enable_pin: !PA13
... # rest of the settings for the extruder
[tmc2209 extruder]
uart_pin: PB8
Now you have told Klipper to use the first slot as extruder and of course you would have to connect your extruder to this slot then.
Only the first [stepper_z] may have the axis defining information like
endstop_pin: ...
position_endstop: ...
position_max: ...
as obviously your z-axis can only have “one truth” regarding the information how far to travel or when to stop.