A simple way to persist parameter values in a Custom Control?


I have some Custom Controls allowing for some printer maintenance operations.
(Do Purge, Go to position, Home+Set Offsets etc.)

But for illustration please consider the "Enable Fan" example from the documentation:

name: Enable Fan
command: M106 S%(speed)s
  - name: Speed (0-255)
    parameter: speed
    default: 255
        min: 0
        max: 255

Problem statement:
I want the 'speed' value to be persistent such that the value I typed and used (submitted) will be retained and will show up in the next Octoprint execution session as 'speed's default value (instead of the hard-coded default value stated in the Control's body)

If there's no simple way to accomplish this, maybe there is a simple way to at least obtain this default value from some existing auxiliary file? (JSON or whatever)

Many thanks!