Display user defined fields on system forms

Hi all,

my question is the following:

Is there any possibility to display user defined fields on the main form of a document instead of the side window?

Here's a screenshot for a clearer view of the issue:

Furthermore, I'd also like to know if it's possible to use the 'choose from list' selection mode on user defined fields instead of formatted search?

If so, what's the technique for achieving this? Can it be done without addon development?

If not, will it be available in the future versions?

Thanks in advance for the answers and kind regards.