Since early 2019 I have written a number of blogs here on GeoNet. Most of these posts cover tips and tricks on the use of the ArcGIS API for JavaScript 4.x. And, since I am still playing around with this API, more contributions will surely follow. A considerable number of my posts are written in Dutch, my mother tongue, but some are in English.
Below you will find a (growing) list of the tutorials in English.
For an overview of the tutorials in Dutch, you can have a look here: https://community.esri.com/people/EPolle_TensingInternational/blog/2019/06/02/aan-de-slag-met-arcgis...
Tutorials - ArcGIS API for JavaScript 4.x
