EDIT

For orphan taxa "open in... " presents the possibility NameEditor but this results in a ClassCastException:

last remote method : http://api.cybertaxonomy.org:80/flora-cuba/remoting/common.service
last remote request client time : 2021-02-10T14:50:24.366
last remote request response header time : Wed, 10 Feb 2021 14:50:24 GMT
client error time : 2021-02-10T14:50:30.556
login : w.berendsohn
editor version : 5.19.0
server : api.cybertaxonomy.org (cybertaxonomy.org) / flora-cuba
schema version : 5.18.6.0.20201124
os : Windows 10 10.0 amd64
java : 1.8.0_251
org.eclipse.e4.core.di.InjectionException: java.lang.ClassCastException: eu.etaxonomy.cdm.persistence.dto.UuidAndTitleCache cannot be cast to eu.etaxonomy.cdm.model.taxon.TaxonBase
                at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:65)
                at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:282)
                at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:288)
                at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:264)
                at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:132)
                at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.execute(HandlerServiceHandler.java:152)
                at org.eclipse.core.commands.Command.executeWithChecks(Command.java:494)
                at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:488)
                at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(HandlerServiceImpl.java:210)
                at org.eclipse.e4.ui.workbench.renderers.swt.HandledContributionItem.executeItem(HandledContributionItem.java:433)
                at org.eclipse.e4.ui.workbench.renderers.swt.AbstractContributionItem.handleWidgetSelection(AbstractContributionItem.java:454)
                at org.eclipse.e4.ui.workbench.renderers.swt.AbstractContributionItem$3.handleEvent(AbstractContributionItem.java:482)
                at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
                at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4418)
                at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1079)
                at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4236)
                at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3824)
                at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1121)
                at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
                at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1022)
                at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:150)
                at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:693)
                at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
                at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:610)
                at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
                at eu.etaxonomy.taxeditor.Application.start(Application.java:20)
                at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
                at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
                at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
                at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)
                at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
                at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
                at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
                at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
                at java.lang.reflect.Method.invoke(Unknown Source)
                at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:673)
                at org.eclipse.equinox.launcher.Main.basicRun(Main.java:610)
                at org.eclipse.equinox.launcher.Main.run(Main.java:1519)
Caused by: java.lang.ClassCastException: eu.etaxonomy.cdm.persistence.dto.UuidAndTitleCache cannot be cast to eu.etaxonomy.cdm.model.taxon.TaxonBase
                at eu.etaxonomy.taxeditor.editor.handler.defaultHandler.DefaultOpenTaxonEditorForTaxonBaseHandler.open(DefaultOpenTaxonEditorForTaxonBaseHandler.java:1)
                at eu.etaxonomy.taxeditor.handler.defaultHandler.e4.DefaultOpenHandlerBaseE4.execute(DefaultOpenHandlerBaseE4.java:47)
                at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
                at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
                at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
                at java.lang.reflect.Method.invoke(Unknown Source)
                at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:55)
                ... 37 more