I recently purchase a new construction home that utilizes PEX plumbing - which is completely new to me. If you look at the picture below, this 3-way split (1/2" pipe) on the cold water is going to a toilet, a sink, and the refrigerator. I would like to completely disconnect the refrigerator line because I am hooking it up to a separate reverse osmosis system. What do I need to do at this 3-way split to properly close it off? Is there some sort of screw-on plug and/or will I need to use some of the blue plumber's dope to ensure a tight seal?

I hired a plumber to have fix few pipe issues. He did not fasten screws and he attached brass ferrule to plastic tubing (this was for ice maker). Any way was a leak under sink and I did not see it. Next day my neighbor complained about leaking roof. I called this plumber again he came back and fixed issue. But he would not listen to damage he has caused downstairs and who will pay for it or whether he has liability insurance. Now he is avoiding my phone calls. I know each situation is different. What are my options. Should I file complain with BBB? Or how does state plumbing license works? Any suggestions please!