The role of script editor is an interesting one around these here parts. Quite a few people call themselves that or offer their services as such... but my impression is that there are very few truly qualified script editors out there in Australia.
What script editing is not, is rewriting someone's script for them. What it should be is helping the writer realise their vision.
I actually like reading other people's scripts and offering suggestions and giving feedback. I think I'm pretty good at it. One day I should even think about charging for it... especially when I see some of the "script editors" who do.
But for now it's a good way to keep up craft skills - nutting out why something isn't working or how to improve elements of a script is a good skill set to have in your tool box. It's also good karma. Plus you get to talk to other writers and be energised by their passion and their stories. It's one of the main reasons I like PAC Script Lab so much.
The great irony, of course, is that the clarity you bring to someone else's script may be tragically missing when you look at your own work. Something about wood/trees I suspect!
I only have one actual credit as a script editor - for the short film Kanowna. To be fair, my main contribution was to tell that director to stop pestering me and write the damn thing himself. Which, to his merit, he did. All I did was suggest a few rearrangements and the paring back of dialogue. He saw the film so clearly in his head that it was basically a case of capturing those scenes on paper.
Otherwise, I've had producers ask me to read scripts/treatments and/or meet with a writer; there are one or two close friends who will invariably run things past me; and occasionally I am fortunate enough to sit on funding or judging panels.
What I think people may not realise is how much time and attention it takes. I always, Always, ALWAYS read the script wanting to discover a story that captures my imagination, entertains me, takes me to a world I may know nothing about. The analytical side is banished on the initial read through - I want to be dazzled by the magic of the storytelling. Worrying about structure and turning points and character and theme and... and... and... all comes later.
But that means a minimum of two reads...which takes time. You're also thinking about all the elements that make up a good story and assessing (second read onwards) what is working (always important to give positive feedback) and what needs attention (the constructive feedback). Then you generally ask a lot of questions to work out what the writer's vision actually is and compare that to what's on the page
It's all good fun (a relative term for a screenwriter... trust me!) and something I gladly do for people who I respect and have some form or professional relationship with. Paid editing gigs would be nice but money isn't a driving motivation - I guess it's a love of the craft - as corny as that may sound - and helping fellow writers. I know how hard it is to be in the trenches trying to create magic from a blank piece of paper.
That's not to say everything I suggest is adopted - far from it. Some of the best discussions are where the writer gets a better understanding of his/her work through 'strenuous debate' or where a suggestion triggers other ideas.
The only disheartening side is sometimes - not often - you spend that time, you take due care and attention, you offer quality feedback and it's taken for granted. No acknowledgement, sometimes not even a simple thank you. When that happens you shrug, trust in karma and hope you helped make the project better whilst trying not to take the lack of response personally.
Finally, I always treat the writer the way I would want to be treated in the same situation. It can be traumatic putting something you have created out into the world. The only goal must be to put aside ego and make the work better. That can be damn hard but film-making is the most collaborative of mediums and a screenwriter has to be both flexible and develop a thick exterior to weather the inevitable buffeting as the script evolves and gets better. After all, all writing is rewriting...