There is no convenient way to select a single issue on the plan view without opening the detail view. This is a regression from previous versions.

The Release Notes state:

https://confluence.atlassian.com/display/AGILE/JIRA+Agile+6.5+Release+Notes
Clicking a card automatically opens the issue detail view — Previously, clicking a card would select it, but not open the issue detail view. You can still select a card without opening the issue view by using cmd/shift-click.

However, ctrl-click will add the clicked row to your selection, and shift-click will add the rows between your current selection and the clicked row to the selection.

The only workflow that allows the user to click on a row, manipulate it, then click on another row, and not open the detail view (e.g. for the purposes of ranking) is to right click on a row, then left click on the same row.

As a user, I want to be able to click on a row in plan mode on my agile board without opening the detail pane so that I can maximize screen real estate and avoid losing my place in the list as it re-sizes to accommodate the detail view.