Sets whether tool_item is visible when the toolbar is docked
vertically. Some tool items, such as text entries, are too wide to be
useful on a vertically docked toolbar. If visible_vertical is FALSE
tool_item will not appear on toolbars that are docked vertically.
Since 2.4
Sets whether tool_item is visible when the toolbar is docked vertically. Some tool items, such as text entries, are too wide to be useful on a vertically docked toolbar. If visible_vertical is FALSE tool_item will not appear on toolbars that are docked vertically. Since 2.4