Features used to implement the example

• Update issue fields
• Copy parsed text to a field

Example: Set priority for issues that have been in a certain status for longer than 24 hours

I'm going to answer publicly to a question I have receiver by private email but that may be of interest for all users of the plugin. The question is:

We are going to do it in two steps:

We use post-function Copy parsed text to a field to set virtual field "Ephemeral string 1" with the name of the priority we want to use:

We use post-function Update issue fields to set virtual field "Priority" with the value stored in "Ephemeral string 1" in all issues returned by the following JQL query:
status = "In Progress" and status was "In Progress" before -1d

Once configured, the transition configuration will look like this: