I am just starting to work with Experience Builder so forgive me if this is a rudimentary question.
In the basic list widget and adding dynamic content, should I be able to see and select the custom arcade expressions that I have configured for the popups for the layer in the web map?
If so, could someone tell or a screenshot of where I should see them (because I am not).
Note: the layer is being pulled from our ArcGIS server (map service). Not a portal, just a plain ArcGIS server map service.
I don't really follow on where you problem is but have you looked into the documentation of the widget?
Try following this video, see if it helps you -