Hi Stephane Bergeron,
Thank you for reaching out to us.
You can edit the DTSX file using Visual Studio. The issue linked below provides a detailed explanation on how to open a DTSX file in Visual Studio.
https://free.blessedness.top/en-us/answers/questions/1096955/open-a-dtsx-file-in-design-view
If you need any more help, please let us know. We are happy to assist.
Thanks & Regards,
Rekha Athmakuri.