You are welcome. To clarify, if you create a folder in the symlink folder and navigate to it, it looks like it is that path. For example if you go to the testlink above, create a directory, navigate into that directory - it will show c:\temp\testlink\newfolder in the explorer address bar. In fact any folder in there whether created through the symlink or directly through the shared path, will look local when accessed through the symlink.
Interestingly when you target the symlink to make a new symlink - it creates it just fine.
New-Item -ItemType SymbolicLink -path C:\Temp\Linktest\Linktest1 -Target \\server2\share\folder\in\share
Of course it creates it in the actual target folder. I thought that was interesting. So I guess to correct my answer, yes you can add a subfolder - it will exist in the target folder. Regarding “appending” to the symlink, if you really need a directory before the symbolic link and it needs to actually be local, you’d need to delete the symlink so you could create a folder with the same name as previously stated. Unfortunately you can’t do New-Item -ItemType SymbolicLink -Path c:\temp\testlink1\testlink1 -Target \server\share\folder unless c:\temp\testlink1 already exists.