DON'T is the initial answer when it comes to deploying individual .42m. However there are times when the change is minor, there is a sense of urgency, and the destination may not necessarily be a production system where making a change to the .4gl, recompiling it, and deploying the resultant .42m is the action to take rather than triggering a full recompile and deploy.
To learn more about what should go into your decision making when faced with this scenario , read
https://4js.com/ask-reuben/ig-82/