Since making marmalade involves cooking fruit and pectin and juices at a particular temperature for a specified amount of time, can you use sous vide to mimic this process and make and can marmalade in this way?
It depends on what you are planning to do.
If you want to get shelf-stable marmalade without a strict canning process, the answer is absolutely no. This kind of marmalade means that you're basically cooking a concentrated sugar syrup, and you have to keep it at the boiling point in an open vessel for a sufficient time for the water to evaporate.
If you want to use a modern marmalade recipe for canning, the answer is also practically no. Canning recipes have to be tested for safety, and are only safe if prepared exactly as prescribed. If it is made for stovetop, you can't guarantee that all relevant parameters will stay the same. Theoretically, it's conceivable that some experts will design a recipe specifically for sous vide and will test it properly before publishing it. If you have found such a recipe and trust it, then you could follow it. But I think they are very unlikely to exist, given the cost/benefit ratio of both the design process and of making the marmalade itself.
If shelf stability is not needed, then the answer becomes yes. You can experiment away with cooking a marmalade in a sous vide machine, either starting from a traditional stovetop recipe, or designing your own. From the viewpoint of food safety, the result will have to be kept in the fridge and eaten within 5 days.