Hi Francois,
Thanks for contacting Syncfusion support.
Query1: I can't make component MultiSelect work when EnablePersistence="true".
We have already considered the reported issue as bug in our end. The fix will be included in the upcoming patch release which is expected to be rolled out on or before end of June 2021. You can track the status using the below feedback link.
Query2: When I arrive in a page, what is the best event to retrieve the persisted data from the MultiSelect ?
The best way is to achieve using the property EnablePersistance. Once the fix the has been included, you can achieve your requirement using this property and we will let you know once the fix has been included in our end.
We appreciate your patience until then.
Regards,
Ponmani M