No no, no problem now.
In fact if you drag the extension into the main page of CHROME you have a msgbox at the left down of the page a little bit like this "Attention extension can corrupt your computer"
You have two button "continue" and "cancel"
If i click on continue, there are a yellow banner in the top "Extensions and user scripts can't be added except from Chrome webStore"
It's a protection for the site who added extension without allow of the user.
So if i do tools/extension and drag the JS in the extension page..that's works fine
The only thing i have forgotten it's reboot CHROME for the extension works
Now, i search how not collapse automatically the code.
Since all the time, i have the behaviour to look the code in his integrality with a little glance
And now i'm forced to click on the + button for see the full code
Again thank for your precious help, now i can copy/paste the splendid code of all the members in one clic
