Can one who missed Maariv at night and needs to Daven Tashlumin by Shachris be the Chazan and have his Chazaras Hashatz count towards his Tashlumin?[1]

Yes. In the event that one needs to make up a Tashlumin prayer and he is serving as the Chazan for the current prayer, then upon his recital of the repetition he is to have in mind to fulfill his Tashlumin prayer with it, in addition to his intent to repeat the prayer for the sake of fulfilling the obligation of those who are not expert in the prayer. [When Davening Chazaras Hashatz as a Chiyuv of Tashlumin, one is not obligated to recite Elokaiy Nitzor quietly at the end of his repetition, although he should take three steps back.[2]]

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[1] See Admur 108:6; M”B 108:6; Ketzos Hashulchan 28:2; Piskeiy Teshuvos 89:6

[2] Piskeiy Teshuvos 122:3; To note however that in such a case many are accustomed to recite Elokaiy Netzor despite it being a Tircha Detzibura. Vetzaruch Iyun as to their source; See Admur 122:1 for the background of Elokaiy Netzor.