How to print out more than 20 items (documents) in MongoDB's shell?

DBQuery.shellBatchSize = 300

will do.

MongoDB Docs - Configure the mongo Shell - Change the mongo Shell Batch Size

From the shell if you want to show all results you could do db.collection.find().toArray() to get all results without it.

You can use it inside of the shell to iterate over the next 20 results. Just type it if you see "has more" and you will see the next 20 items.