Can I modify a scheduled report that I did from the standard reports?

Yes, you can modify the scheduled report that you've created by going to the Manage workflows section. From there, you can copy, turn off, or delete workflows at any time.

Here's how:

1. Go to the Gear icon.
2. Select Manage workflows, under TOOLS.
3. In the My workflows column,  find the workflow you want to edit.
4. In the Actions column, click the ▼ dropdown and choose Edit.  
5. Make your changes, then select Save or Save and turn on.

Don't hesitate to reply here if you have more questions.