The issue was caused by the Vaadin update to version 8.12.3 https://github.com/vaadin/framework/pull/12203 and fixed in Vaadin 8.1.2.4 by https://github.com/vaadin/framework/pull/12221

Steps to reproduce

in Config app, select e.g. /server/admin, hit ENTER, then SHIFT+TAB or TAB

Expected results

One should be able to cycle through nodes and properties. See also https://docs.magnolia-cms.com/product-docs/Authoring/Keyboard-shortcuts.html#Keyboardshortcuts-Editingitems

Actual results

Upon hitting SHIFT+TAB or TAB, cell is no longer editable and cycling doesn't work

This can be seen in UI tests too (temporarily disabled)

• KeyboardShortcutUITest#itIsPossibleToCycleBetweenPropertiesAndNodes
• KeyboardShortcutUITest#selectionIsOnCorrectRowWhenCyclingUsingTab

Development notes

• Action target is null when hitting (SHIFT+)TAB at info.magnolia.ui.workbench.tree.TreeViewImpl.EditingKeyboardHandler#handleAction(Action action, Object sender, Object target)
• changeset between Vaadin 8.9.4 and 8.12.3 https://github.com/vaadin/framework/compare/8.9.4...8.12.3