Features used to implement the example

• Update issue fields
• Write field on linked issues or sub-tasks

Example: Moving sub-tasks to "Open" status when parent issue moves to "In Progress"

We see provision in Jira Workflow Toolbox to change parent issue's status when a sub-task's status changes. Similarly, is there a way to change a sub-task's status when its' parent issue's status changes? For instance, if parent  issue status changes to "In Progress" , sub-task status change to "Open". 

Yes, you can do it inserting Write field on linked issues or sub-tasks or Update issue fields post-function in transition "Start Progress" of parent's workflow. In the case of Update issue fields you should use the following configuration:

Once configured, the transition will look like this: