When you say your manager won’t let you do it, you’re effectively looking for a place to hide.
Why?
Because you want somebody else to make the decision for you. And if the decision works out, you’ll take the credit and if it fails your boss will have to take the blame because he/she supported you in doing what you wanted to do.
If you want to do something, take responsibility and do it. Without seeking endorsement from your authority. If it works, you’ll be able to showcase what you did, and if you fail very few will know anyway.
When you take responsibility yourself, you’re in the box to make it a success or failure. If you’re trying to do something new then the odds of failure are more. But, don’t let that stop you. There is much learning to be gained from failure than from success.
If you want to shine, stop hiding and take responsibility for doing what you want to do.