How do you set a seed, or entropy, or default string, for keys generated by Web Crypto, please, anything to make it deterministic

It is surprisingly difficult to set the entropy, or seed, for the Web Crypto API in javascript.

Why is this the case? Is it to make things difficult for developers?

Setting seeds allows you to deterministically run on sample data. The Web Crypto API also happens to be baked in to the library i am using. This feature of the library that i am trying to implement has also been almost abandoned because of how difficult this problem is.