As far as I'm aware there is no default tool in Mendix to allow you to manage focus, you would have to rely on a widget or js/jQuery.
Here's a small example with jQuery "$('.my-field').focus();" you can drop this in an HTML snippet widget as jQuery and it should do the trick.
Hope this helps
focus helper widget https://marketplace.mendix.com/link/component/107276
Thanks for you reply. I understand that I can use js/jquery but how do I trigger it from a standard Mendix event - like conditional show, click on btn etc? We really try and stay away from custom widgets.