@Override
				public boolean isEnabledForContext(ActionContext context) {
					if (currentFunction == null) {
						return false;
					}

					Object contextObject = context.getContextObject();
					if (!(contextObject instanceof GTree)) {
						return false;
					}

					GTree gTree = (GTree) contextObject;
					TreePath[] selectionPaths = gTree.getSelectionPaths();
					return selectionPaths.length > 0;
				}
A variable used to restrict open-ended operations, like expanding all nodes or filtering.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/calltree/CallTreeProvider.java