More information, it looks like I was barking up the wrong tree, you don't seem to need the 'UML2 End-User features' add in.
You can right click and create new UML2 Model Diagram.
while I have successfully created UML2 Class Diagram, I am seeing issues when trying to create Sequence Diagram.
I posted bug in bugzilla, as I thought issue was with the UML2 PLug in, but they have correctly pointed out that the issue is in genuitec's code.
Summary of issue
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Steps to Reproduce:
1. Create Class diagram using New UML2 class diagram
2. Add some classes
3. Now click on class and in context menu select 'Generate UML2 Sequence
Diagram'
4. Now select Merge with existing model
5. get Invalid UML2 Model Path, with following null pointer exception
java.lang.NullPointerException
at
com.genuitec.eclipse.uml2.ui.wizards.pages.Java2SequenceDiagramWizardPage$3$1.select(Java2SequenceDiagramWizardPage.java:261)
at
com.genuitec.eclipse.uml2.ui.wizards.pages.Java2SequenceDiagramWizardPage$3$1.select(Java2SequenceDiagramWizardPage.java:266)
at org.eclipse.jface.viewers.ViewerFilter.filter(ViewerFilter.java:51)
at
org.eclipse.ui.dialogs.ElementTreeSelectionDialog.evaluateIfTreeEmpty(ElementTreeSelectionDialog.java:375)
at
org.eclipse.ui.dialogs.ElementTreeSelectionDialog.open(ElementTreeSelectionDialog.java:219)
at
com.genuitec.eclipse.uml2.ui.wizards.pages.Java2SequenceDiagramWizardPage$3.widgetSelected(Java2SequenceDiagramWizardPage.java:279)
at
org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:228)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1598)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1622)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1607)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1396)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3484)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3068)
at org.eclipse.jface.window.Window.runEventLoop(Window.java:825)
at org.eclipse.jface.window.Window.open(Window.java:801)
at
com.genuitec.eclipse.uml2.ui.actions.Java2SequenceDiagramAction.run(Java2SequenceDiagramAction.java:47)
at org.eclipse.ui.internal.PluginAction.runWithEvent(PluginAction.java:251)
at
org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
at
org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501)
at
org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1598)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1622)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1607)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1396)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3484)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3068)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2405)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
at
org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at
org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at
org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
at
org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
at
org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at
org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at
org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
at
org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
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Here is link to full bug -
https://bugs.eclipse.org/bugs/show_bug.cgi?id=311003