Good morning Atick.
Yes, exactly: I was unable to adjust the width of module positions because the pop-up no longer appears.
The impact on the layout or design of my project because of this issue is that I could not change the width of the modules.
More specific: I could not change 8,4 into 7,5 or 9,3
BUT
This morning I dared to use the button "default" which is on the left.
(after making an Akeeba)
The "default" repaired my error.
Everything works again!
Thank you for the time to look into this.
I hope someone else can use my solution
Dick