Ver 3.1.3
I was setting up to do a demo on charts and was really confused because I distinctly remember using Arcade the last time I used a chart, and I couldn't find the option this time.
And then it hit me: This data is a Query Layer. So I pull in the plain table to check. Same thing, I can't find it. So I export to SHP and Bingo, the Arcade button is back. See below:
File GDB: Arcade

SHP: Arcade

Enterprise GDB: No Arcade???

Please add in this functionality, if it isn't already in a future release.