How to access from the Browser to the HTML-Player?

Hi

We are building a HTML-Build for playing a Scene in a Web-Browser.
We search for a way to access from the **Browserside **into the Player (actually the WebGL-Renderer in the HTML Canvas-Element).

The reason is:
We would like to create our own HTML/css/js-Menue and sending/trigger from outside some values into the Player.

Example:
We have a button in the HTML-File which should trigger a Blueprint-Event in the Player that changes the cameraposition.

We have found Plugins like WebUI or html-menus but WebUI only works for Desktop Builds and not for HTML-Builds (we are not sure yet about html-menus but we guess it will not work as well).
And they are closed, which means they cannot be accessed from outside.

Has anybody an idea how to access to the HTML-Player from outside?

Kind regards