Welcome and thanks for reaching out to the Community, @Siddhartha.
In QuickBooks Online (QBO), the ability to pull up a report by sales representative is currently unavailable. This is only available in the desktop version (QBDT).
If you used the Class tracking feature to associate it with the sales rep, you can add itcolumn in the report as a workaround. This can be done by clicking the Customize option at the top right and placing a checkmark on the Class box in the Rows/Columns drop-down.
While this option isn't available yet, rest assured that I'll pass along your suggestion to our Product Developers. They're always looking for ideas to consider on how to improve QBO. In the meantime, I recommend visiting our Blog site. This is where we share recent happenings and future developments, such as updates to newly added features.