Object update vs. Object.set

I did feel off the paved path when I found & used Object.set I’m trying to use a query-string library and I’ve written the following ReScript binding:

type queryString = {parse: string => Js.Dict.t<string>, stringify: Js.Dict.t<string> => string}
@module("query-string") external queryString: queryString = "default"

type location = {search: string}
@scope("window") @val external location: location = "location"

let params = () => queryString.parse(location.search)

Then at my call site, I’m doing something like

let dict = QueryString.params()
Dict.set(dict, "key", "value")

RescriptReactRouter.push(
  pathString ++ "?" ++ queryString.stringify(queryStringRecord),
)

How can I do something similar without needing Dict.set?