Hello @ioa747
Assuming your AutoIt version is 3.3.16.1, maybe you got files that need to be updated in your Scite folder / subfolders.
For example, if these 2 files "au3.api" and "au3.keywords.properties" got a modification year indicating 2018 (in Windows Explorer) then it could explain why some actual functions names are not found in them.
Then you won't find these functions in the autocompletion list (while you type the beginning of their names in Scite), also their color won't be the same as the other functions names (as you noticed when opening Array.au3)
In case @Jos reads this, he could tell you how to solve your problem, in his own helping words
Have a great week-end