In the dashboard designer, when I create a pivot table, I want to set the default width. Right now I have to drag the column width manually to expand it. How do I set a default width for the column in the pivot table (like how I can do it in Collections)?

You can set the default width for columns in a pivot table, by editing your Dashboard in the Dashboard editor. 

• In your dashboard builder select the dashboard you would like to edit. This opens up the Dashboard Editor. 
• In your Dashboard Editor, you can select your pivot table. 
• The pivot table side navigation opens up
• Under display properties you can modify the width, the higheit, or placement of the pivot table.