Once you've created a BOQ or Sub-Location you can Edit/Update the details at any point and here's how!
First you'll want to navigate to the Layers portion of the Measure Tool, then look for the Update BOQ button on the right hand side - The buttons will be in line with the associated BOQ/Sub-Location.
Now click on the Pen Icon associated with the BOQ or Sub-Location you wish to update.
A popup will appear with editable fields relating to the BOQ/Sub-Location. Go through and update any details you wish to change and once you've finished updating them, simply select the UPDATE button at the bottom of the popup window.
Pro Tip
Editing a Sub-Location will subsequently update all associated BOQ's related to that particular Sub-Location.