Consider using a contextual menu item instead.
DisplayHelpTopic "DataBrowserObjectsPopup Menu"That's available since IP9 and gets around some peculiar legacy behavior that using buttons gives you.
I think you may be able to use ModifyBrowser echoCommands=0 to turn off printing the commands, but whether your button code should do that is questionable, since that doesn't apply only to your button but more generally to the Data Browser.