Pretty sure you should be doing the refresh before trying to query and update the repeater from the cms with your filters.
But saying that I cannot see why you are refreshing the dataset and then querying the cms.
I would expect you to then use the refreshed dataset.
This should save you Having to re filter and query the cms again.
wixWindowFrontend.openLightbox('Ajout Suppléments')
.then(async () => {
let numResaValue = $w('#NumResa').value;
// == Refresh datasets to latest CMS data
await $w('#SupplementsResa').refresh();
await $w('#ResaEnCours').refresh();
// == wait for dataset to be ready
await $w('#SupplementsResa').onReadyAsync();
await $w('#ResaEnCours').onReadyAsync();
// Now use new data
$w("#supplementsRepeater").data = $w("#SupplementsResa").getCurrentItems();
$w("#resaRepeater").data = $w("#ResaEnCours").getCurrentItems();
});
Not tested…