Why are Z probe types 1,2,3 and 5 only available for Z probe 0 ?

[MaxGyver]

On my CNC I have two Z-Probes. The first probe is a simple switch that is permanently fixed in one table corner and is used as a tool length sensor (AKA toolsetter) The second probe is a 3D-Probe for probing the Workpiece XY and Z zero coordinates. Example on a StepcraftCNC

I am using a Duet3 6XD with RRF 3.5-rc.1
In my config, I have configured the probes as follows:

; Z-Probe
M558 K0 P5 C"io3.in" H180 F600:60 T6000 ; create probe #1 (toolsetter)
G31 K0 P500 X0 Y0 Z0                    ; set Z probe trigger value, offset and trigger height

M558 K1 P5 C"io4.in" H180 F600:60 T6000 ; create probe #2 (3D-Probe)
G31 K1 P500 X0 Y0 Z0                    ; set Z probe trigger value, offset and trigger height

Now on startup i receive the following error:
"Error in start-up file macro line 52: Types 1,2,3 and 5 are available for Z probe 0 only"

[dc42]

@MaxGyver those Z probe types use a filtered analog input. As analog probes are rare now, when we added support for multiple Z probes we didn't add additional filters for more Z probes, to economise on RAM.

Type 5 is a filtered digital probe. You can normally use type 8 with digital probes.

[MaxGyver]

@dc42 Ah okay, that's great!