I personally also suggest KeePass2 for an offline vault storage that you can use with Syncthing to synchronize so the data never leaves your devices.
It’s worth mentioning that both these programs are subject to leaks in machines infected with malware like OP’s was, so maybe if malware is a problem you deal with regularly, i suggest the online options.
I think you overvalue the skillset of border security. This may seem trivial to you but it’s uncommon to hire people trained to this level of competence and put them at every point of entry. A decent cybersecurity investigator needs a big salary.
That would probably happen if you were already a suspect of something or a high profile person and they moved in resources for you. No way border security is randomly sweeping for headers and entropy, they basically just look at it with the explorer and clone it, possibly using some software to scan for known security vulnerabilities to access encrypted parts. That would be a court ordered search or a high profile crime investigation, or maybe a really really unlucky day where the expert was already there for another reason, but the rest i agree.
If your threat model makes you a high profile person, then smuggling data in hidden containers is definitely not the best solution. A non associated personal cloud server is best.
US companies and helping genocide for money, name a more iconic duo. Forget IBM and the Nazis, prepare for Google and the Zionazis.