This looks like a CHM. What output are you using?
I believe RTL is supported in HTML5 and WebHelp. Does it work as expected with those outputs? - Beware that for WebHelp, you have to use one of the RTL skins from the gallery.
My output is an HTML Help, it is a project I have imported from a previous version of Robohelp.
To generate a HTML5 format, I need first to understand how to do because this format is not visible in the list of possible outputs. I can see it on New project but not on imported project. I need to make more search to be able to build a HTML5.
I have found how to create the Output HTML5 and you are right, the index is displayed correctly with this format.
Is it only supported by this output?
The generated help need to be distributed with the installer of a software and it supports today only 1 help file.