I figured a workaround, by adding
fieldname=* fieldname2=* to the search, it added them to the output in fast mode. I would like to still find a way to force it to verbose mode in a dashboard if that is possible.
I don't think so there is an option in Simple xml to change search mode (in advanced xml, yes). Your solution is more of best practice than workaround.
You could try adjusting the settings for the saved search that drives this visualization. In savedsearches.conf, there is a display.page.search.mode setting that allows you to set the mode.
See also this previous Answers discussion for more info and possible limitations on the setting:
Hope this helps!
Ran into the same basic problem, and still can't find any explicit support for "Verbose" mode in Simple XML as of Splunk 6.5. However, that being said, a very simple but effective work around is to simply add a
| fields * to your search.
<base search> | fields * | ...