Start writing, or don't get sidetracked?

If you're 60% through your novel, then that means you've already put in a lot of hard work, so why not continue with till the end? Personally I try to not think about other book ideas until I'm at least nearly finished with my WIP. Also, when you say 60% through, do you mean 60% through with your first draft? If so keep in mind there's yet a hard road of work ahead of you in the editing/revising process, so you may not be 60% done, but instead more like 20% done (or even less). Regardless, focus on your current book and try to push all other ideas aside. It's not that hard, at least not for me. Working on a book requires much concentration and brainpower; use your energy wisely. But if you have some really cool ideas that can somehow fit into your current story, you can try that, too. Good luck!

Maybe therein lies the solution to your problem: don't revise so much until you've completed the draft. I like to edit and revise while I work, too, but only enough to help me not lose track of the story and keep it more or less orderly. Push through to the end. I'd say it's highly likely you'll be revising/editing/changing stuff in your current 60% several more times still, so don't worry about that part so much now. If the story hasn't been written yet, that means nothing is final.

You're in the middle. It's a common place to feel like the whole thing is crap, and the shiny new idea is better. Only problem is that if you abandon this project, the shiny new project will hit the same slog at roughly the same point, and a new shiny new project will come along and whisk you away to what will surely be The One... until you hit the same patch in that one.

Point being, there's a good chance you should just push through and finish this one. Then set it aside and work on Shiny New, and once you have *that* draft finished, go back to the first project and work through edits.

Yes, restriction. I've been telling myself that once I finish this second draft I can start planning a new book. Of course, I can't stop the occasional thought.
Also, don't go back and edit your work. When I get to the second draft most of that "edited" stuff will go anyway.

I suggest jotting down your new ideas (doing it here counts if you'll remember to check!) then keep going as quickly as you can through your current project.

Ideas are easier to handle when they're new. I have several novel partials that stop 50% to 75% into the latest draft for each. Those stories were set aside when major life changes sidetracked me. Going back into a long work after a long break is painful.

Tell the witch to wait or else she might be dumped for the next thing.

I find that completing writing gives me more skills that I wouldn't dream of. Ditto that to editing.

EVEN if it never gets published, it makes me a better writer. For that reason alone, it is worth it.

Agreeing with the others who advise writing down the shiny new so you don't forget it, then lock it in the plot bunny closet without carrots (and for the love, don't get it wet) until you finish the current project. I find that when I have something shiny new pop up, it helps me to outline out the idea in my 'closet' aka OneNote - I'll also sometimes make a Pinterest board and a music playlist to capture the visuals and the mood for the story as I currently see it, which will make it easier to get back into when it's time to actually write it at a later point in time.

But then seriously, lock that sucker up and chuck the key somewhere dark.

Stick with your current love. Your characters (besides the one you hate) will see you through!

That's great that you have these wonderful, creative ideas swirling around your head (your idea in the OP sounds inriguing and different). That feeling is exciting--it's heady. But in order to make anything out of these ideas, you have to motion one to the fore and concentrate on it until it's a fully formed thing, while the others remain in the background. It's not bad or unhealthy to have other ideas at the same time. Some of those may turn out to be viable projects, some may not. But they have to wait until you've given this one your full attention, and that means seeing it through to the end of the first draft. Keep notes of those cool ideas, then let them come to the fore when it's their turn. You might find that, unbeknownst to you, your mind has been working on some of these ideas in the background, and when you come back to it consciously, boom, the ideas start flowing.

It's perfectly alright to edit as you go, by the way. Just don't let it be an endless cycle.

Finishing a draft (first is usually hardest, but second/third/etc have their own challenges) is always going to be a different thing than whatever the idea that came to you was. Not just because ideas change as the story gets fleshed out and refined, but there will always be sloggy bits. (Even if you enjoy the thing you're writing there's always a point when you start to wonder if you'll ever be done.

Today I'm working on a draft of a thing I first started (and finished one really, really, really rough draft of) back in 2009. I've been poking at it ever since trying to resolve some gaps in the plot that I couldn't quite get a handle on. (Fingers crossed that this time I've figured it out.) I loved the idea at the time, I've loved working on it since, but I just couldn't get it to work. If you're stumped, it's okay to set something aside for a while. If you're just tired of it... that's going to happen probably every time, so picking up a new idea will only delay the inevitable.

(I actually wrote a thing about this last month on my Patreon about knowing when to push through and finish something - because that's a valuable skill and a difference maker when it comes to success as a writer - and when to take a break because you're burning out. So, I won't say you have to finish it, because that's not always the right solution. But if it's just Shiny Idea-itis, try and stick with it until you get the draft finished before taking a break.)

There's nothing saying you can't get to those ideas at a later time. If you don't start on them this instant, then they aren't going anywhere. Finish what you're doing, maybe take a bit of time to flesh out those ideas while you write (and finish!) something else. That way, you've finished what you're currently working on, and you're in a better position to start on new ideas when the time is right to start on a new idea.

That's how I do. I have ideas for two major projects in mind, that I'm slowly fleshing out, while I'm plotting out my next novel, and working on the query for my previous novel. Learning to balance projects (and time) is a very useful skill to teach yourself.

So is fidelity to one project.

Sometimes it can be good to get out your new ideas by writing them down - I find it really helpful to completely outline and plot new ideas before going back to the work I'm mostly done with, so that when I do finish that work I have a proper outline to sit down with immediately and get writing.

I'd say if you finish your first draft then start writing your next idea in earnest - it might help you go back to the first draft with fresher eyes.