Have Different Source Content Across Languages
In most localization projects, an source language file (say, English) is used which is translated in other languages. The English file will have 100 specific phrases, and all other languages will have those 100 phrases translated.There are cases which need a more advanced method of localization, where the source content changes depending on the target language.
The most frequent case is when your content is very different between languages. For example, on your Global homepage you talk about your product in a generic way, but on the French version of your homepage, you show the Eiffel Tower and have a new paragraph talking about the beautiful cafés of Paris.
Another case, slightly different but with similar solution, is when you want to change your content depending on a segmentation of your users. For example, you may want to say "Hey there John!" to your users with ages 10-25, "Hi John" for ages 25-50 and "Hello John" to the ones above 50.
You have a number of ways to tackle these issues.
"Fork" the page in French
After you've finished creating the page in English, you can copy it as a new page in your CMS and translate it. Then, add the content specific to French. Done! (Note, in this case, you need people to actually create the content in French directly (eg. a French marketing person).
This is the most simple approach with the cost of unmanageable future edits. The French page now has its own content. If something changes in the English page, it'd be hard to apply those changes in the French page, since its now its own page with its own source content.
Different source files depending on target language
In this case, you can author two different English pages (in English): one targeting everyone, and another one targeting the French audience. The latter's content will still be English, since it's easier for you to write content in English. Now you have two different source files. The second one has an additional paragraph mentioning the Eiffel tower.
Now you can localize the first file in all languages except French, and the second file only to French.
In Transifex, you can save these two files as two different resources or two whole different projects. We recommend the latter, since you can add more files than just the one we talked about.
Combine everything in one master English file
You can create one master English file which contains the union of the phrases from all languages. That is, phrases common between all languages and the ones which are specific to French.
This is a simple solution, often easy to code. Developers might include all phrases in the code and collect them all in a single file. The challenge this approach has is that the source language file is more complex, the flow of content is lost and translators will probably get confused.