TxxxItemEditor - descendant

Given the tumultuous reactions to my posts, I would like to create descendants of these three classes.
I also need to insert one CheckBox there.
If possible, how can this be done?

I suggest to have a look at the source code of the 3 different sample editors like TPeriodItemEditor wheren you can see in PlanPeriodEdit.pas that it descends from TCustomItemEditor.

If I understood correctly, the easiest way would be:
Use your PlanxxxEdit units
Rename units and classes as needed
Edit forms and classes
Create and install the bpl package.

It is correct? Will I violate your license?

You can do it this way and it is not violating any license.

I adjusted it like this:
2021 01 15 18 51 02

procedure TSimplePlannerItemEditForm.chk_SimpleShapeClick(Sender: TObject);
begin
  CBShape.Items.Clear;

  if TCheckBox(Sender).Checked then
  begin
    CBShape.Items.Add('Kruh');
    CBShape.Items.Add('Trojuholník');
    CBShape.Items.Add('Hor. šípka');
    CBShape.Items.Add('Ver. šípka');
    CBShape.Items.Add('Trojuholníky');
    CBShape.Items.Add('Kruhy');
    CBShape.Items.Add('Štvorce');
  end
  else
  begin
    CBShape.Items.Add('Obdĺžnik');
    CBShape.Items.Add('Zaoblené');
    CBShape.Items.Add('Šesťhran');
  end;
end;type or paste code here

Is it possible to increase ItemIndex by 10 when writing to DB here (if chk_SimpleShape.Checked)?
Or I have to do it in the application in the event
procedure TfrmPlannerRole.dbpmwMonthItemToFields(Sender: TObject; Fields: TFields; Item: TPlannerItem);

The ItemToFields and FieldsToItem event are the place where you would customize how you read & write TPlannerItem property values to a DB field.

Thanks, I knew that. I wanted to get around it.
The CheckBox path is blind.
I close the topic.