The problem is not solved. I was aware of these options before asking my question.
This is not fair to others who search for the same answer. Your own documentation is misleading users by presenting examples which you’ve yourself claimed are not secure. ( fetch, jQuery, XHR )
Why not simply explain the reason SeaTable will not allow submitting JSON data directly from my game ?
You already noticed by yourself in your second post that it is not a good idea to use JavaScript because this will expose your credentials. Therefore, three different individuals told you that you should think of another solution.
You write that you develop web games. Then it should be an easy task for you to create a small PHP, python or whatever script to receive the data of your web app game and then use the API to write the data to your base.