"How to make Tasklist's save button store vars in engine" GitHub example doesn't play in my case

Hi folks,

I’ve recently tried to apply @falko.menge’s GitHub example here

so as to make Tasklist’s Save button save the current state of my task form but for some reason doesn’t play :neutral_face:
The only difference that I noticed (in the following screenshot below) is that when I switch to History tab of my task form, I see the timestamps when the variable has been modified by the assignee user of the task. Inside variable’s inspection in Cockpit app, I can see only the saved values from the 1st modification of the variable and not also from the 2nd one.
When I come back to Tasklist, the task form is empty from values.

Could anyone please help me on this ?

Thank you in advance,
Steve