Whoa!  That looks familiar!  :)

With Maui, you normallly don't need to do methods like #sortedNotes.  You can just have #notes in there like you do at the bottom (set its output resultView to #panel).  Then if you simply implement these methods on your Note class:

    mauiDefaultColumns

        ^ #(med date heures com)

and

    mauiSortableColumns

       ^ #(med date heures comString)

and

    comString

        ^ self com ifNil: [ String empty ]

Then, hover your mouse inside the yellowish area of the collection, press ESC to invoke the menu, then select "generate heading".

You will get proper headers for those columns with ascending / descending sort arrows for each column.  All for free from Maui.

HTH.