I want a career in video editing, can any editors advise on what certification I need and what type of work experience will impress future employers?

As the owner of a video production company, where you went to school is not nearly as important to me as what you can show me, namely your reel. When beginning in video production & editing, gaining experience is the most important priority. The 2 most common ways are to go to film school or start by yourself with tutorials from Google/YouTube.
I am not going to cover film schools but you can do a local search if that is your interest. Depending on your financial resources you can shoot your own video and then practice editing it. Another excellent inexpensive asset is to buy stock footage from a stock footage company like VideoBlocks and practice editing with others content. Once you have your basic skills in place you can contact local video production companies and request to intern with them, a common intern relationship allows you work alongside a production crew to gain real life professional experience on paid projects, you can generally include your contributions in your reel. If possible, make yourself available to be on shoots as well so you get to understand both sides of filmmaking.
The last thing to consider is if you want to freelance or work in a production house, you may want to wait to decide until after interning and having the experience working for a production company. Many times as you gain competency, you can make the switch from intern into paid position within the same company. The simple truth is that as your skills increase so does your

demand and other opportunities which often lead to side projects when employedfulltime in production.