Hi @ablovatto,
It looks like the show and hide buttons have been removed from the plugin in the latest version.
If you press SHIFT + O while looking at the ticket you’ll notice that the buttons don’t appear in vanilla osTicket either.
But if you go to Admin Panel > Manage > Plugins > Attachment Inline > Instance > select your instance > Config
…you’ll see the following option:
Hide Seen:
When auto-showing an attachment, store the ID in the users browser, so they can choose to see it again if they want, but are not forced to.