It is possible to load a session plugin using the session plugin preset feature. After you create a session plugin preset, you could make a UI Button in a new scene and add a button trigger to load the preset, as shown in the example image below to load a present titled "new." In this case, the "new" preset has a clock plugin and another editing plugin as examples. This button trigger will load the plugin(s) to the scene plugin area though, not the session plugin area. Whether or not you could then reload or activate some aspect of the plugin would depend on the interface of the particular plugin. I could make more images to step thru the entire process if you would like.
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