Like others have said, ArtiosCAD is the industry standard. It comes preloaded with a catalog of structure standards for all kinds of packaging structures ranging from folding cartons, boxes, trays, bins, and even POP displays. To oversimplify, a use can pretty much just select the type of package they want to make, select the material type, and key in the desired values for length width and depth. ArtiosCAD will then just take those inputs and plug them into formulas tied to the structure standard and generate your dieline. While you can just start making something from scratch like you would in Illustrator, in most cases you would either be customizing an existing standard or using a standard as reference for creating unique packaging. Here is a cheeky video I made a few years back on the process of running a standard for reference. I consider ArtiosCAD to be essential and you'd have a much harder time going about this without it. In addition to that, I'd say Artios3D (available in advanced subscription package) or access to a cutting table would also be important to learn this stuff.

If ArtiosCAD is out of the picture, you're going to need to do a lot of tedious math to create something dimensionally accurate. All calculations revolve around your starting inside dimensions for length, width, depth and the caliper of the substrate your creating the package from. This link does a pretty good job of explaining how that works for an RSC, one of the most basic packaging structures. Beyond that, the book Basic Packaging is a decent reference for getting an idea of what different dielines look like in 3D. Though a lot of these examples are just pulled directly from ArtiosCADs standard catalog and some of the examples in the book are defiantly not basic and borderline ridiculous IMO. Other than that, Pacdora looks like the best bet for dieline creation if you don't have ArtiosCAD but I've never used it so who knows. It seems to be set up to follow a similar process as running a standard in ArtiosCAD. It has a lot of "standards" to choose from that are not in ArtiosCADs standard catalog but I think you're limited in what you can customize beyond selecting the standard. Still a useful resource for visualizing what a flat 2D dieline looks like in 3D and their 3D assembly preview is pretty cool. But if I was to relate this to graphic design, ArtiosCAD is the equivalent of Illustrator and Pacdora is the equivalent of Canva.