In my project I have a custom field, project picker type. I want that everytime I choose a project in this custom field an issue is created in that project that I've chosen.
I'm working in server and I have scriptrunner installed.
How can I do it?
So this is pretty close: https://library.adaptavist.com/entity/automate-the-creation-of-an-issue-in-jira
The adjustments you'll need are
1. to do it as a post-function or listener (depends on exactly how you want to trigger the creation of the issue - your question reads like you want to do it every time the field changes on an issue, which I'm not sure is what you mean. If it is, then you'll want a listener to catch "edit" events as well as maybe transitions)
2. Instead of the hard-coded project id, read your custom field. A project picker should hand you a project object directly when you use getCustomFieldValue so you'd be able to replace the project = componentaccessort-etc stuff with that