A few fixes to make the plugin work again, might not be everything but it's the core stuff...
Fix for userInfo not being applied to connections group. Removing the pluginIdentifier solved the problem, and it's not necessary Sketch applies the plugin invoking the action as identifier by default.
Fix for "doc.selectedLayers().layers is not a function". Dropping .layers() solved the problem.
Fix for "Can't find variable: MSLayerArray". Removed MSLayerArray.arrayWithLayers and simply passing the layer objects seems to work fine.
Fix for "connectionsGroup.deselectLayerAndParent is not a function". Simply removed this function, without it the user selections are retained despite the folder being added.
A few fixes to make the plugin work again, might not be everything but it's the core stuff...