The Field Maps Designer's Arcade profile/version should match the current Arcade version available in the latest Field Maps mobile application release. That way is something works in the Designer we know it will work in the field.
I have noticed that within the Field Maps designer, the Arcade functions available in field calculations do not match what can actually be executed in the Field Maps application, creating a false expectation of what actually works in the field. I suspect that the Designer uses the AGOL profile (currently on version 1.26) while the actual mobile application is, I think, 1.19 since Field maps on iOS runs on ArcGIS Runtime SDK 100.15.
For example - I was excited to try the "PointToCoordinate" Function to get M-values on the fly in the field. In the Field Maps Designer, and in a Web Map, it works perfectly, but in Field Maps I get an "unknown function" error.
