Hello,
Custom filters can be created with the help of the “Woodmart Woocommerce Layered Nav Widget” in Appearance -> Widgets: https://prnt.sc/0MDWkfB8UcZz in which you can define to which attribute the filter will be activated: https://prnt.sc/vwpgHApG42IZ
So firstly create an attribute in Products -> Attributes, then define that created attribute to some products and create the mentioned above widget. As a result, you will have the custom Filter.
Don’t hesitate to let me know if you need any further help or any other info
Kind Regards