FileBot

For my format, I use this It works perfectly, giving me collections that exist. However, if a file belongs to no existing collection, how can I automate grouping it into a collection that might happen later on i.e when a title receives a sequel after it's been sorted as an individual title. Is there a way to rescan the finished files later and hardlink move titles into the new collection.

You'd effecitvely have to organize your entire collection once again:
viewtopic.php?t=4788

When re-processing files, avoid unnecessary load on TheMovieDB services, exclude files that are already in a collection folder, files that are older than X years, etc. Maybe once every few months. Do not re-process your files every day.