Clear / Purge selected values in dashboard

Hello Gurus!

I'm currently working on Dashboard BI4.1 (SP2) connected with BEX queries.

After adding a new query, we need to fill the prompt to run it. I have few prompts, included one based on the profit center which is mandatory.

I'm using a prompt selector to display the hierarchy to the users. This prompt is link to 4 others queries.

So far so good...

When I saved it and export to the launchpad, it keeps the values (for all prompts) that I filled in the query browser.

-->Do you know how to purge the prompts ? like in Webi?

I change the preferences to uncheck "Save Query Result with document"... without success.

Thanks for your help!

PS: sorry but I don't find any topics about this basic question!