You can use the Document Grid to display different data, and filter and sort results.
Once you have selected the rows containing the set of peptides that you want to delete from the document, you can use the "Actions" dropdown at the top of the Document Grid to delete the peptides associated with the selected rows.
If you want to learn more about the Document Grid, you should take a look at the Custom Reports tutorial:
The Actions dropdown is a relatively new feature and is not covered by the Custom Reports tutorial, but the tutorial will talk about adding columns to a report and filtering and sorting.
The rdotp value in the Customize Report dialog is called "DotProductLightToHeavy". You can find it at:
Proteins > Peptides > Peptide Results > DotProductLightToHeavy