The update links are
http://www.civil4d.com/2008/10/restoring-classic-layer-filters/
and
http://www.civil4d.com/2009/06/layer-filters-2010/
Just in case, here is the copied text
Thank you for contacting Autodesk Support. Unfortunately, the Import/Export layer Functionality was removed from Civil 3D 2009. However, have a workaround that will hopefully meet your needs.
There is a command called CLASSICLAYER. This command should bring you the older Layer Manager with all of the commands. However, to get this to work correctly, we need to modify the Registry slightly. To add the required Windows Registry:
1. On the Start menu (Windows), click Run.
2. In the Run dialog box, enter regedit. Click OK.
3. Find the following subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R17.2\ACAD-7000:409\Applications\AcLayer\Extensions
4. Double-click the ADT String Value.
5. In the Edit String dialog box, in the Value Data text box, enter AecLayerManagerEx.dll and click OK.
The next time you launch Civil 3D, type CLASSICLAYER. You should now get a new dialog box that has the correct commands. Keep in mind that the “old” civil layer manager will still function as before. You can modify the CUI to add a button or change the Layer Toolbar to launch this Classic Layer Manager instead, although it will not be dockable.
For 2010 on 32 bit OS
HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R18.0\ACAD-8000:409\Applications\AcLayer\Extensions
For 2010 on 64 bit OS
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Autodesk\AutoCAD\R18.0\ACAD-8000:409\Applications\AcLayer\Extensions
For 2011
HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R18.1\ACAD-9000:409\Applications\AcLayer\Extensions
for 2012
HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R18.2\ACAD-A000:409\Applications\AcLayer\Extensions
As Matthew says in this post, the change does not work on the classic layer manager in 2010 and above but works on the new layer manager.
If a post provides a fix for your issue, click on "Accept as Solution" to help other users find solutions to problems they might have that are similar to yours.
Andrew Puller
Maitland, NSW, Australia
Windows 11
Intel core i7 11800 @ 2.30 GHz with 32GB Ram
Civil 3d 2023