Error "not possible to add a collection" with digiKam 5.7.0 in Win7-64

[Hans Schmidts (WEB)]

Same error with alternative syntax
"\\.\D:\Backup\..."
(other alternative syntax like "\\?\Device\HarddiskVolume3\Backup\..." 
and "\\.\Volume{b1a6d4c4-f117-11e4-a0c2-806e6f6e6963}\Backup\..." do not 
work), but successful with localhost:
"\\localhost\d$\Backup\..."

Is this a known bug, is there another workaround than using network 
share? I expect that access via network share is slower, and it's 
annoying, that path selected via folder select dialogue does not work.