This article explains how to view & update plans from the portfolios page.
The Portfolios page is editable. Add any columns to the view you want to edit. If the field is editable and you have permissions to edit that item, click on the desired field to change. Certain fields may not be available for certain plan types, based on configuration. In that case, you won't be able to edit the value.
Plan Contextual Menu
Select the contextual menu for a plan to see the available planning modules and options for that plan. Based on the plan's type & stage, certain features may be enabled or not.
Select Quick Edit from the plan's contextual menu. On the right side of the screen, the plan's details form appears, condensed to one column. Scroll up & down for the plan fields. The form is editable and your edits save automatically.