Supreme Court very clearly said a staff on Administration on Justice, such as Registry Staff can not exercise Judicial functions.

From Paras 9 and 10,

9. The nature of judicial function is well settled under our legal system. Judicial function is the duty to act judicially, which invests with that character. The distinguishing factor which separates administrative and judicial function is the duty and authority to act judicially. Judicial function may thus be defined as the process of considering the proposal, opposition and then arriving at a decision upon the same on consideration of facts and circumstances according to the rules of reason and justice. A Constitution Bench of five judges in Jaswant Sugar Mills Ltd., Meerut vs. Lakshmichand and Ors., AIR 1963 SC 677, formulated the following criteria to ascertain whether a decision or or an act is judicial function or not, in the following manner

(1) it is in substance a determination upon investigation of a question by the application of objective standards to facts found in the light of preexisting legal rule;
(2) it declares rights or imposes upon parties obligations affecting their civil rights; and
(3) that the investigation is subject to certain procedural attributes contemplating an opportunity of presenting its case to a party, ascertainment of facts by means of evidence if a dispute be on questions of fact, and if the dispute be on question of law on the presentation of legal argument, and a decision resulting in the disposal of the matter on findings based upon those questions of law and fact.
                                             (emphasis added)
The act of numbering a petition is purely administrative. The objections taken by the Madras High Court Registry on the aspect of maintainability requires judicial application of mind by utilizing appropriate judicial standard. Moreover, the wordings of Section 18A of the SC/ST Act itself indicates
at application of judicial mind. In this context, we accept the statement of the Attorney General, that the determination in this case is a judicial function and the High Court Registry could not have rejected the numbering.

10. Therefore, we hold that the High Court Registry could not have exercised such judicial power to answer the maintainability of the petition, when the same was in the realm of the Court. As the power of judicial function cannot be delegated to the Registry, we cannot sustain the order, rejecting the numbering/registration of the Petition, by the Madras High Court Registry. Accordingly, the Madras High Court Registry is directed to number the petition and place it before an appropriate bench.

Citations: [2019 (2) Crimes 321], [2019 (2) JLJR 279], [2019 (2) KLJ 955], [2019 (2) PLJR 291], [2019 (2) RCR (Civil) 767], [2019 (2) RCR (Criminal) 767], [2019 (6) Scale 465], [2019 All.M.R.(Cri.) 3493], [(2019) 9 SCC 154], [2019 SCC ONLINE SC 507]

Other Sources:

https://indiankanoon.org/doc/85097973/

https://www.casemine.com/judgement/in/5ca8c17e9eff430a58956741

https://www.vakilno1.com/supreme-court-of-india/high-court-registry-cannot-question-maintainability-of-petition-supreme-court.html