I suppose you go via FRA? Tell them guys at the airport a couple of days before you're checking in a "weapon" and you are totally clueless as what to do. They are gonna be happy to help you and less prone to cause any trouble. Just sayin...
German knive law states you may carry any knife (7.5 cm max for folders, 12 cm max for fixed) in any way (open or concealed) unless the type of knife is explicitly forbidden. You cannot carry (readily accessible on your person in pocket, sheath or other method) a one handed opening and locking knife (Choose one or the other) unless you can prove a "valid interest". This would be sports, hunting, camping, religious purpose or job (Kitchen, leatherworking), sharpening service or from the store where you just bought it. (Note that self defense is NOT a valid interest) Not being able to show this purpose when carrying, it isn't a felony but more like a parking ticket - but you will loose the knife to the state. To transport these legally owned knives. they must be in a locked container and not readily accessible.
While in reality this isn't enforced unless you are acting like a total idiot, be aware of these laws.
Forbidden is carrying any knife in temporary social settings, like fairs, gatherings, sports events.
Certain knives are completely forbidden. These are knives explicitly designed and built as weapons. (entering felony territory here). These are balisongs, automatics and gravity knives where the blade flys out the front, stilettos or daggers of any sort, knives with two sharpened edges, throwing stars and "camouflaged" knives like cane or belt buckle knives. Some of these are illegal weapons and some you may own but not carry because there is no "valid interest". Example: A dagger is never a hunting knife.
Now the above is not the complete end all description for German knife law but we can figure the following: You are basically breaking the law edcing most of your knives for the purpose of edcing. This means if you transport them to the airport in a non-locked container (locked suitcase is fine) and check them and/or are having a
very unlucky day, you WILL lose them.
Buy a container that you can lock (cheapest is fine) and a TSA approved lock (stateside issues) and you are good to go. You do not need to declare checked knifes because unless forbidden, they are legally classified as tools.
Examples of knives you can totally legally edc in Germany, open or concealed would be: Any fixed blades up to 12 cm (crk ps), slipjoints or nail nick folders (new mnandi, buck 110, sak, opinels). You can also remove thumb studs or fill spyderco holes to be "legal".
Just like stateside, depending on where you are, knives are seen as normal tools or "weapons". Stuttgart is not very critical in this regard and nobody "should" give you troubles. I'd carry any of your above knives as EDC there but I'd keep in mind that it "could" be some trouble.