SidebarEx & SidebarPerNamespace Extensions incompatible to 1.20

[audiocommander]

These two important extensions are incompatible to 1.20 and should be replaced by either features of the template or a new custom extension

• [ ] update extension or
• [ ] write own new extension (take list from a special named wiki page and insert as html widget)

[jdittrich]

might be worth a try (and not to be broken in future): a css based solution using css namespace detection and display:none or display:block