When I go to Customize report there is no filter drop down menu. Why?

Let me help you with this, info384.

The Filter drop-down menu won't show up on the report if you're using QuickBooks Online Simple Start. Please see the attached screenshot below for your guidance.

 

This feature is available in the Essentials, Plus, and Advanced version of the product.

Also, please refer to this article, Reports included in your QuickBooks Online subscription to learn which reports are available for your versions.

You can upgrade your subscription if you want to use the filter functions. To do so, simply follow the steps listed below for your guidance:

1. Go to the Gear ⚙ icon at the right top.
2. Select Accounts and Settings under Your Company.
3. Choose Billing & Subscription from the left navigation menu.
4. On the QuickBooks Online section, click Upgrade.
5. Choose the plan you want, then click Upgrade again.
6. Confirm the payment information, then click Save.

I've added a quick tutorial below for additional guidance with the steps above.

I'd appreciate if you can tell me the report you want to customize. It'll help me provide the exact report needed to show the information you need.