Timeout on M291return default value

[OwenD]

I'm loving the great flexibility that the new M291 functions bring.
At present if you use a timeout value (Tnn), the result is to cancel the macro.
I would like to request this be altered slightly such that if a default value is specified then that value be returned as the input after the timeout.
If no default is specified then the current cancel after timeout setup remain.
I see this as opening up possibilities where for non critical events can be acted upon differently.
Lets say (off the top of my head) that a filament runout is detected.
You could have something like this.

; filament runout detected
M25 ; pause print
M400
M291 S4 R"Change filament" P"Filament runout - go to standby temp?" K{"No","Yes",} F1 J1 T120
if input = 1
	M568 P{state.currentTool} A1
	echo "Tool set to standby temperature"
	M116
M291 S3 P"Press OK to resume print"
M568 P{state.currentTool} A2
M116
M24 ; resume print

If I'm near the printer I can change the filament without "cooking" the filament in the hotend
If I'm not nearby to take immediate action then it goes to standby and waits.
This is just an example to illustrate easily.

[T3P3Tony]

@OwenD

I have opened a FR on github for this: https://github.com/Duet3D/RepRapFirmware/issues/891

T3P3 created this issue in Duet3D/RepRapFirmware

open [FeatureRequest]: Timeout on M291return default value #891