This is the answer from D-Link Help:
Going through your email we would like to inform you that you cannot hide the SSID in a repeater mode but you can try the following workaroud to hide the SSID:
Step 1 Change the visibility status of the wireless network to invisible in router mode on the DIR-505 and save the settings.
Step 2 Now when you switch the DIR-505 to a repeater mode, the SSID will remain hidden.
Should you require further assistance with your D-Link products, please reply to this message, or call toll free at 877-453-5465.
Thank you for networking with D-Link .
I haven't tried it in router mode yet. In Hotpot mode doesn't work, so I suppose it would be the same result in router mode also.
If i would try, I will post it.