After installing 'U Gui Proxy Full' from ecosystem, console insists on the following:
Assets/PlayMaker DataMaker/Xml/__internal__/Editor/DataMakerActionEditorUtils.cs(379,65): error CS0117: `HutongGames.PlayMaker.Ecosystem.Utils.PlayMakerInspectorUtils' does not contain a definition for `SetActionEditorArrayVariableSelectionContext'
Edit: I deleted DataMaker and PM UGUI folders and reinstalled in opposite order; PM UGUI first, then DataMaker, which seems to have fixed it for now.