To clarify, Dorje Shugden is not the only Dharmapala manifesting 5 forms. Many other Protectors also have this. Palden Lhamo for instance even has a special jenang for all 5 Mothers, and we make offerings, praises, and special requests to them in her Kangso.
It's a little surprising people didn't know Dorje Shugden 5 lineages is the 5 Buddha Families since it is explicit in the Kangso and commentaries.
It is also worth mentioning here that Dorje Shugden's mandala is the body mandala of Guhyasamaja. In the Gelug lineage, the three main Yidams are important: Heruka Chakrasamvara, Vajrabhairava (Yamantaka), and Guhyasamaja. There are many ways to receive the special blessings of all three.
For instance, self-generating as Heruka, regarding Dorje Shugden as Yamantaka, and recalling the mandala is the body mandala of Guhyasamaja. If we generate as Vajrayogini, it is the same as just mentioned because she is the same person as Heruka. If our Yidam is Yamantaka, then it is particularly important to regard Dorje Shugden as the nature of Heruka, and remember the mandala of deities is Guhyasamaja body mandala. It may seem insignificant, but Manjushri was very explicit to Lama Tsongkhapa about the importance of receiving the blessings of all three. It may seem insignificant to merely recall someone is the nature of Heruka, but it is very profound especially when we sit with the knowledge for more than two seconds. If you do not already, I highly recommend sitting for a while in the presence of Dorje Shugden and his retinue contemplating and delighting in the knowledge that this is Guhyasamaja's body mandala. Wonderful!