How to swap JSON property with another from variable?

Question

I have two JSON files, A.json and B.json.

A.json

{
  "ui": {
    "strings": {
      ...
      ...
    }
  }
}

B.json

{
  ...
  ...
  "metadata": {
    ...
    ...
    "ui": {
      "strings": {
        ...
        ...
      }
    }
  }
}

From A.json, I grab the ui key:

myVar=$(jq '.ui' A.json)

I would like to now replace B's ui key's with myVar. Can I get assistance with this?