Opening index.html in the Delphi IDE

WEB Core generates an index.html file, and the various videos I see show it being opened in the Delphi IDE.

I’m running D10.4.2 and when I try to open this file in any way I can think of, I get an IDE error and I have to close the IDE. It just chokes.

Is this fairly normal for 10.4.2?

Or is there something interfering with its ability to open a text file or html file or ...?

We are not aware of issues.
Do you first save the project (i.e. with all its files, including the project HTML file) before opening it for editing?