I am not sure if Associated Domains feature is doable, but I believe the feature to pass a function handler when pressing “Confirm” on keyboard can be done, since that is actually implemented in AppleLib, and its construction (including invocation method) is same comparing to iOSKit-existing SKProductsRequest. It is my fault that I am not familiar with iOS programming at all, and thus I am not sure how to implement it on Xojo - but I am sure SKProductsRequest has the same constructing way comparing to textFieldShouldEndEditing:. This is previously discussed in this thread, but there is no more discussion in this thread for using textFieldShouldEndEditing: as a native way of handling it.
Hope this can be added to iOSTextField 