How to get id from context filter in views?

Please tell me how can I get the node id from the url in views? Is it possible to pull it out of the context filter so that after passing it to the form via the prepopulate module? I am creating a website for accounting books in the library. I have three types of materials: reader, book and issue. There are 4 fields in the issue: a link to the reader, a link to the book and two dates - issue and return. When I design a book for the reader, I create the issue material. My main task at this stage is to implement the creation of an issue with the book and reader fields filled in in the form of creating material. To do this, I created a block view with books that are not on hand. In this view there is a connection with the issue and a filter by the absence of the value of the book field in the issue. This view is on the reader's page. Also in the view there is a custom text field with a link to the form where I add the book id. I also need to pass the id of the reader on whose page we are in order to add it to the same link.