100% - that’s called slicing (to make interlocking designs), and the adustable slots are parametric.
Any of the 3D softwares will do it - but they do have a fairly steep learning curve. You can also do it by hand, but that’s, as you indicated, much harder!
If you’re solely a hobby user Fusion360 has a free license. I don’t know if Cuttle does slicing, but it’s certainly powerful enough to (hey @tobyschachman, can you weigh in?) I know lots of folks used 123Make, but that no longer exists, Autodesk is suggesting TinkerCAD which I have no experience with.
Search those terms here on the forum and you’ll find lots of discussions!
This one may be of particular interest: