Suppose Flash content settings is set to "Block". When right-click on the placeholder of blocked flash content, "Run this plugin" contextmenu command is disabled. In Slimjet 13 and Chromium 58 I can manually activate flash content by this command.
If Flash content settings is set to "Ask", SJ will only ask once the first time it encounter flash content after startup. Then it will run flash content on all web sites without asking.