If you right click the PurePaths dashlet and go to Dashlet Properties, there is a section called "Columns" which allows you to customise what columns should be displayed in each of the tables of the PurePaths dashlet.
That being said, you are limited to just some out-of-the-box options, you can't add any thing you want.
Hope this helps.
Roberta, I'm not sure I understand your use case. BTs are aggregated views grouping data by some attribute. So if each row of the BT shows a different IP address, then what does it mean to show the Start/End time of a set of PPs. Perhaps I've missed something.
For the PurePaths dashlet - it's a fixed list of options you can include.
For Business Transactions, any measure added to the Results section will have its own column inside the Business Transaction Results Dashlet.
Start time is not an option since a Business Transaction does not show individual occurrences of transactions, but instead aggregates all data within the timeframe. However, if you drill-down to PurePaths from the Business Transaction Results you will get the individual PurePaths each marked (by default) with the start time. End time is only available via Start Time + Response Time.