v2.1.0 onward WCPT PRO now provide the facility to create multi-range slider for your custom field and price filter elements. You can now provide visitors a convenient way to select multiple numeric options in a range. If you are using an attribute, you need to switch it to a custom field.
Note: This facility works on all major browsers including Microsoft Edge v80 but not on earlier versions of Edge or IE.
Attribute filter workaround
The multi-range slider is no available for attribute filter right now. This is due to complications with the way woocommerce stores data for product attributes which makes it inefficient for this purpose.
Instead, what you can do is to store the specific attribute as custom fields as well on each product. Now you can use that custom field to provide a multi range slider filter (as well as sorting if you need).
Going to each product page and saving the attribute as a custom field can be time consuming. There are more efficient ways to accomplish this, covered in this doc.
Once you have the attribute saved as a custom field, you can proceed with creating a custom field filter and using the multi-range slider in that element.
Settings to create custom field range slider
The settings for Price range filter are very similar.