@jay_s_uk Hi! It's my first time using Duet2, so if you could help me a little more would be great. From your answer, I understood that i should modify the config.g and create a new axis. But, where do i connect the drive? And how do i map it with the new axis?
Here is my config.g if it's usefull

; Configuration file for Duet WiFi (firmware version 3.3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.3.16 on Wed May 31 2023 17:09:22 GMT-0300 (hora estándar de Argentina)

; General preferences
G90 ; send absolute coordinates...
M83 ; ...but relative extruder moves
M550 P"My Printer" ; set printer name

; Network
M552 S1 ; enable network
M586 P0 S1 ; enable HTTP
M586 P1 S0 ; disable FTP
M586 P2 S0 ; disable Telnet

; Drives
M569 P0 S1 ; physical drive 0 goes forwards
M569 P1 S0 ; physical drive 1 goes forwards
M569 P2 S1 ; physical drive 2 goes forwards
M569 P3 S1 ; physical drive 3 goes forwards
M584 X0 Y1 Z2 E03 ; set drive mapping
M350 X256 Y256 Z256 I0 ; configure microstepping without interpolation
M350 E256 I1 ; configure microstepping with interpolation
M92 X12800.00 Y12800.00 Z12800.00 E12800.00 ; set steps per mm
M566 X900.00 Y900.00 Z60.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z180.00 E1200.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z20.00 E250.00 ; set accelerations (mm/s^2)
M906 X800 Y800 Z800 E800 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 E00 S1 ; set axis minima
M208 X288 Y147 Z38 E035 S0 ; set axis maxima

; Endstops
M574 X1 S1 P"xstop" ; configure switch-type (e.g. microswitch) endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop" ; configure switch-type (e.g. microswitch) endstop for low end on Y via pin ystop
M574 Z1 S1 P"zstop" ; configure switch-type (e.g. microswitch) endstop for low end on Z via pin ystop
M574 E01 S1 P"e0stop" ; configure switch-type (e.g. microswitch) endstop for low end on E0 via pin e0stop

; Z-Probe
M558 P1 C"zprobe.in" H5 F120 T6000 ; set Z probe type to unmodulated and the dive height + speeds
G31 P500 X0 Y0 Z2.5 ; set Z probe trigger value, offset and trigger height
M557 X15:215 Y15:195 S20 ; define mesh grid

; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B1 S1.00 ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0 ; map heated bed to heater 0
M143 H0 S120 ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T100000 B4138 ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit
M143 H1 S280 ; set temperature limit for heater 1 to 280C

; Fans
M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1 ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500 ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45 ; set fan 1 value. Thermostatic control is turned on

; Tools
M563 P0 D0 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined

Thank you for answering so quickly! Looking forward for yor reply.

We are using the Duet 2 Wifi for a threedimensional 3D printer, excepting that we added a 4th axis. It has a stepper motor with a syringe on it, and an endstop too (connected on the E0 pins). We're having trouble setting up that endstop, for making the homing process. We accomplished to move the E0 motor when doing the "homeall" process, but when the endstop gets clicked the motor doesn't stop.

this is the configuration of the homeall:
G91 ; relative positioning
G1 H2 Z5 F6000 ; lift Z relative to current position
G1 H1 X-235 Y-215 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
G1 H2 X5 Y5 F6000 ; go back a few mm
G1 H1 X-235 Y-215 F360 ; move slowly to X and Y axis endstops once more (second pass)
G1 H1 Z-205 F360 ; move Z down stopping at the endstop

T0 ; Select tool 0 for use (syringe) this enable the commands in Dashboard
G1 H1 E0-40 F60 ; move E0 (Syringe) 10mm down in 60mm/min = 1mm/s (first pass)
;M18 E0 ; stop E0 axis when it hits the endstop
G90 ; absolute positioning
;G92 Z0 E0 ; set Z position to axis minimum (you may want to adjust this)

; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 Z5 F100 ; lift Z relative to current position
;G90 ; absolute positioning

Thank you for reading, waiting for your answer!