This is a very interesting discussion. I ahve a new MB E220d with NTG 5.5. W213 and I cannot insert any POI into the navigation system. There is not any menu or option which let me to insert any POI. I contacted to official service and they told me that it is not possible. For sure, I don't believe this.
I don't know if the problem is in the name of the file, the format of SD card, etc... I have tried with FAT32 format, with PersonalPOI name and GPX files, but it doesn't work.
Recently I have discovered that official upgrade of Nav system has to be done with NTFS, otherwise NAV doesn't recognice the software. I tried to use PersonalPOI folder with GPX files (NTFS format in USB) but it doesn't work.
Do you know anything about the NTG 5.5 command online POI's?.