John Joseph Collins discusses the term "Most High" in Daniel 7:18; concludes the plural in the Aramaic is a "plural of manifestations" and should be translated in the singular.
John Joseph Collins, Daniel: A Commentary on the Book of Daniel (Hermeneia—a Critical and Historical Commentary on the Bible; Minneapolis: Fortress Press, 1993), 312 (Logos Bible Software edition)
18. The holy ones of the Most High: The traditional translation of קדישׁי עליונין (“holy ones of the Most High”) assumes that עליונין is used substantivally, presumably to refer to God, who is called עליא in 7:25* and elsewhere in Daniel. The plural עליונין is then explained as a plural of majesty, on the analogy of the Hebrew אלהים. The construct chain is definite because עליונין is considered a proper name. The Hebrew קדושׁי עליון in CD 20:8 may be cited as a parallel, but its value is ambiguous, because it renders “the Most High” by the singular and so does not relieve the anomaly of Dan 7:18.
An alternative translation, “most high holy ones” or “holy ones on high,” has recently been defended by Goldingay, who explains the second term of the construct chain (עליונין) as epexegetical or adjectival. The plural of the second term, then, would correspond with the number of the first. The phrase would be indefinite and is equivalent to קדישׁין עליונין. The Aramaic for “highest,” however, is עליא (plural). עליון is an epithet for the Deity. The plural, then, should be taken as a plural of manifestations and the traditional translation maintained.