I'm not sure what you are saying/asking. But I'll take a shot.
If the plugin is not listed on the 'details' of the layout and does NOT show up as an area when you edit a layout then the only way to "disable" it would be to uninstall it. This is because, the plugin is made to load all the time instead of being added on a per page/layout basis by the user and therefore, is either ON all the time OR 'off' all the time (which means uninstalled)
I looked at the "Simple Gallery Extended" plugin and it loads all the time. This means that the creator did not give the user the option of using it on a per page/layout basis and therefore once it is installed it will always be "ON"
A new release for Typesetter is in the works with a lot of improvements including the ... Read MoreTypesetter 5.1
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