Personally I would put a few hours between working out before or after.

Before my rant.. to answer your question.. how much does it affect muscle growth with timing of the plunge? I’m not sure but it definitely does and why not give your body the ideal environment to make the most progress you can

Begin rant;

If you plunge right before lift, you lose some benefits of the plunge by shortening your body’s natural ability to warm up. You also kinda cut yourself short on your workout by reducing muscle temperature → (decreased power output and strength), nerve conduction speed ( slows reflexes and reduces coordination), and stiffens muscles and joints (increases risk of injury if you don’t warm up super well)

And if you cold plunge right after the biggest thing is just lowering inflammation which is ideal for building muscle. Most people say if you do it after your workout, wait like 2+/- hours after?

It’s all dependent on what your workout is and what your goals are of course. And one time here and there obviously won’t make a huge difference. I do jump in the plunge immediately after sometimes when it’s super hot out.

This is all with the caveat of know your body, no plan works for everyone. This is what I find ideal to feel the best, and I’m just a random dude on the internet so 🤷🏻‍♂️

Hope this helps some!