Hello,
Yes, it is possible to add attributes to a simple product in WooCommerce and use them for filtering without creating product variations.
Go to the Products > Add New page in your WordPress dashboard.
Set the product type to “Simple product”.
Scroll down to the “Product data” section and click on the “Attributes” tab.
Click on the “Custom product attribute” dropdown and select “Add new attribute”.
Click the “Save attributes” button.
Click the “Publish” button to publish your product.
Now you can add the attribute filter to your shop page by going to Appearance > Widgets and adding the “WooCommerce Layered Nav” widget to your desired sidebar.
I hope this helps. Let me know if you have any other questions.
Best Regards.