I have a list that has some workflows and custom actions. I want to move it to the sub-site.
Is it possible to move it with all it's workflows and custom actions?
As a short answer it's not possible where
Export-SPWeb command doesn't export workflows
Import-SPWeb lists first in your destination then backup and restore the workflow as the following.
You have Two option.
Check the details steps at How to get backup of workflow in share point 2013?
Also, If you are working on the same farm