I want to use my blu-ray drive to store my photos offline. Is there a windows desktop application that anyone is using to group/organize and write the photos to disk? It should be able to take multiple folders of images, and write them to desk efficiently such that grouped photos are kepted together while minimizing wasted disk space.
Make sure you look into m-disc blurays they are designed to last a lot longer than regular blurays. As far as sw on windows I would look into CDBurnerXP. It does blurays, and disc spanning; two things you wanted. Also your post should be posted in in https://softwarerecs.stackexchange.com/ not photography.
I'd like to point out that storing to a bare HDD in a dock is cheaper than quality blu-ray media, and the larger capacity makes it more feasible to re-run integrety checks without having to shovle discs through.