You can add a filter by the Product Attributes option you just need to go through the following steps.
- Go to your Shopify Admin Store > App > Searchly.
- Click on Filters and select Manage Filters.
- Click on Add New Filter.
- Add a title, choose a page from display on drop-down then select Product Attribute option from Create Filter Using field.
- You can create a filter by using attributes such as Price, Product Tag, Product Type (In this case). Click Save.
- Run data sync by clicking Data Sync.
Please see this example for reference: