I am generating the output using HTML5 Layout for my French project. I am able to see some tooltip appears translated and some appears in English. I would like to understand which file controls these tooltip strings such that we can manually fix it or guide the translators to translate it. Any thoughts?
The labels are in a language file, there may be multiple depending on how many languages you've set up. How you access it depends on the version of Robohelp you're using, but mostly under Project Settings > Advanced and either LNG File or Labels tab. RH 2019 New is different, and has a Labels option in the Output view.
In Windows Explorer, the file will have the extension LNG.
(On a side note, my high school French remembers 'index' as a french masculine noun meaning 'index'...)