@Nullable
    @Override
    public String getToolTipText(@NotNull DBNNode node, @NotNull Tree tree, @NotNull Event event) {
        if (node instanceof DBNDatabaseNode dbNode) {
            if (isOverObjectStatistics(dbNode, tree, event)) {
                DBSObject object = dbNode.getObject();
                if (object instanceof DBPObjectStatistics statistics && statistics.hasStatistics()) {
                    long statObjectSize = statistics.getStatObjectSize();
                    if (statObjectSize > 0) {
                        String formattedSize;
                        try {
                            DBDDataFormatterProfile profile = object.getDataSource().getContainer().getDataFormatterProfile();
                            DBDDataFormatter formatter = profile.createFormatter(DBDDataFormatter.TYPE_NAME_NUMBER, null);
                            formattedSize = formatter.formatValue(statObjectSize);
                        } catch (Exception e) {
                            formattedSize = String.valueOf(statObjectSize);
                        }
                        return NLS.bind("Object size on disk: {0} bytes", formattedSize);
                    }
                }
            }

            if (node instanceof DBNDataSource) {
                INavigatorNodeActionHandler overActionButton = getActionButton(node, tree, event);
                if (overActionButton != null) {
                    return overActionButton.getNodeActionToolTip(view, node);
                }
            }
        }

        return null;
    }
Statistics node renderer.
Draws connection type marker next to the item name.
Draws item statistics in the right part.
plugins/org.jkiss.dbeaver.ui.navigator/src/org/jkiss/dbeaver/ui/navigator/database/StatisticsNavigatorNodeRenderer.java