Typically, in fixtures such as the BLT’s that will have the nES 7 installed, they are configured as shown in the Spec Sheet (pictured below). Thus the ONE RJ45 jack that the nES 7 has is occupied.
However, the fixture is generally built so that the OTHER RJ45 jack of the nEPS 60 or nPP16, for example, has a Cat5 cable going to an RJ45 Y-Splitter with its two remaining available female ports exposed on the outside of the fixture. That’s where you do the daisy-chaining.
One exception is with the WL fixtures. They will not have an RJ45 Y-Splitter with its two remaining available female ports exposed on the outside of the fixture. Fixtures like these that are often used in stairwells are generally installed in locations where daisy-chaining is difficult or improbable anyhow. It is, though, acceptable to add an RJ45 Y-Adapter (aka "Cat5 Splitter") if desired: