ReyDev's post in how to use Radio Button with "parse => 'mage' " in Widget was marked as the answer
the problem exists on localhost, but in remote server works !!!
ReyDev's post in Template ... is throwing an error in Production mode was marked as the answer
The problem was solved. There were problems in the license section that were resolved after contacting the support department.
ReyDev's post in Some action after a widget is removed was marked as the answer
I solved my problem in another way. But I think this can be useful.
When I add the widget, I add a value to the array that is stored in the settings. I do this when configuring the widget. (configuration() method)
Now I want to remove this value from the array I defined, when deleting the widget. (I thought the delete method would do that)