Jenkins pipeline: do "Declarative: Checkout SCM" step only
As implied by the links in comments, for better or for worse, this behavior is an unavoidable consequence of how Pipeline is designed.  Pipeline configuration changes in your Jenkinsfile cannot be picked up by Jenkins without executing your Pipeline.  This includes things such as adding parameters.

My personal advice is to ensure that your Pipeline jobs are non-destructive, or in other words, to ensure that the worst thing that could possibly happen by running a job is nothing.  This allows you to pick up configuration changes by just running your job after committing the changes to your Jenkinsfile, and then you can simply abort the job (or let it run to completion if it's a short job) with the confidence that you won't break anything.  Then subsequent runs will have your configuration changes available.