The best way to manage many recordings is to connect to your receiver from Windows computer.
If you have a simple home network with one internet router, most likely your computer and receiver will be on the same subnet, so that they can see each other. If you have more complicated network setup, than hopefully you will be able to put them on the same subnet.
To connect from windows pc, please write down the IP address that receiver has. (Menu > Settings > Network Settings)
Open Windows Explorer Or File Manager (Most people know it as My Computer) - then type in the address field \\192.168.0.xxx - basically your receiver ip address.
That should connect to the receiver and show Share - open the share and you will see all drives that are connected to the receiver, both internal and external.
Please go to Record directory and find your recordings. When renaming, remember every recording has two files, the Index (pointer) file and the actual video. Please rename both in order for this to work. First try with one. Don't rename them all at once and then forget which one was the index which one was the video.
Let me know if this worked for you. I will create a video detailing this.