Welcome to the community. Apps and integration always run under the credentials of the user that added the automation to the board. If you want to assign to the person who created the item (the current user) you can only do this though external services like Integromat, Zapier or build your own little app.
Thanks for your reply, I’ve found what I’m looking for. Don’t why I didn’t see it before but this is basically what I wanted to do.