As of firmware version 1.06, it seems that there is no way to use the actual Link to Reflector feature to link to non-REF or non-XRF reflectors.
However, the Link to Reflector option need not be used to establish a link. Instead, the linking can be done the old way, but putting the command in the Your Call Sign option, or by using the Direct Input (UR) option.
Remember, the radio thinks as if it were me: My callsign is the callsign of the current user of the radio, and your callsign is the callsign of whomever I want to talk to, and is placed in the UR field.
Therefore, I can write the name of the reflector in the Your Callsign field followed by the command to link to the reflector.
So if I want to link to, for example, DCS001K, I would write DCS001KL in the UR field. Then I only need to press the transmit button, or key the microphone up, in order to send the command to the repeater.
The alternative option is to first go to menu, then page 2, and select the menu item DV/DD Memory. There, under the item Your Call Sign, I can add a Your Call Sign item, which I can name, for example, Link to DCS001K, and as callsign enter the above-mentioned DCS001KL.
Afterwards, when I press on the TO field in the Digital Radio mode, I can use the Your Call Sign menu item, to select the Link to callsign I previously memorized, and not have to enter the link command by hand.
In GUI, this option will appear a bit differently, since the radio will show a silhouette, instead of a computer when linking to a repeater, but seems to work fine.