It has come to my attention the the link back to this article that originally appeared on the Enkitec.com web site is broken. Knowing that people still find this useful, I've copied it here so that it can be easily found and referenced.
A minor but important change is happening for Oracle Application Express in the forthcoming Oracle Database 12cR2. Specifically, Oracle Application Express will not be installed by default in the Oracle Database. This change was made specifically at our request. We thought the pros far outweighed the cons, and we thought this was good for our customers and consistent with our recommendations.
In this blog post from 2015 I explained how to open a modal window from an item and pass the values back, display a sucess message, etc. This page also contains an item plugin to make it easier to do the whole stuff and avoid hardcoding. I have never published this plugin. Hopefully this functionality is going to be a standard part of 5.1. Now, I was asked to make this working with a file browse item as well.
See this example on how to change the item position. In APEX you can position the buttons after the action bar in an interactive report. However, you can't put the items there. Using jQuery this is easy to achieve.