How to save a Matrix with Super Table in it
In the super table array, there has to be a type there:

"superTableHandle" =&gt; array:5 [
    0 =&gt; array:3 [
      "type" =&gt; 1//the field's id
      "fields" =&gt; array:10 [
        "relatedArticle" =&gt; 325051
        ...
      ]
    ]
    1 =&gt; [...]


For me, this id is 1. It can be found in database by running this SQL

select * from supertableblocktypes;


But I ran the code below before and found out the field's id is 81 which is not working for me, I don't know why

dd(Craft::$app-&gt;fields-&gt;getFieldByHandle('matrixHandle')-&gt;blockTypeFields);