I think there is a very simple solution for this.

In my front end i have a form, and when this form is saved, i redirect to Thank You page. In that page i don't want to display the system-message DONE.

In my template i have the code:
I want to keep that, because i want to view other messages.

How can i ignore or not process the message DONE on safe?

Those "Done" message or "Error" message are produced in the controller in the save() and apply() methods of the concerned table.

The only thing you have to do is to remove the call of the raising message.

If you want only for a particular layout, you can test wich layout is in use and that's all.

Hope it helps.

you can then share your source code for others users

Sorry, but i cannot find the moment that the "Done" message is produced. In the save() and apply() methods in controller no enqueuemessage or RaiseError function is used. In for example the check() method in the table RaiseWarnings are used. But also there i cannot find an enqueuemessage of other messagefunction for 'Done' when saving of the record is succesfull.

Could you please help a little more. I do not have much experience with coding for Joomla.

Sorry I gave you an incorrect answer.

You can find it in :
classes/jcontroller.php

This code is common to all tables.
So for your project, you can pass a parameter to decide if you want the result message or not.

Thank you. I only want the message in the backend, this is my solution in classes/jcontroller.php on several places:

Yes, correct.