I've discovered some things I should mention here.
First, instead of trying to manually enter codes for qTranslate-XT into the content I can simply visit the translated page URL by either using the language selector or directly entering the language code into the URL. Then from the frontend viewing the page I can go to Pro > Edit Page and it will be editing the content in the correct language.
It's still possible to manually enter the codes, for example
[:en]English text[:fr]French text[:] and then when editing the page you can switch languages to edit the other languages later on.
The issue is though that it doesn't properly save the language codes and just seems to save all languages. Meaning it will overwrite all languages with the one currently being edited.
The only remaining issue that I can't figure out seems to be that the Edit with Pro button on the Pro tab when editing a page in the admin does not work. I'm guessing it must be a conflict with qTranslate-XT and maybe a custom i18n-config.json file has to be created but I'm not sure how to do that yet.