In general you don't want governments or just anyone to know you are transacting in Bitcoin and PSBT shows you are in.
PSBT file is relative small, you could always hide it inside regular file (e.g. png or docx).
I really love this idea! It's quite easily possible to store whole papers in jpegs with minimal modification of the look of the image when opened in an image viewer.
Here's an online tool to try
Steganography.
From
https://en.wikipedia.org/wiki/Steganography, very impressive:
Be careful with this. The “art” of Steganography is an arms race between people trying to hide data and people trying to find said data. The later group is much better funded, although they also are facing a more difficult task.
My advice is to try to hide in plain sight. I would assume that any government can decrypt anything that you possess at the border. Governments have broad authority at border crossings and they have great technology that in many cases is not publicly known.
If you are crossing a border, my advice would be as follows:
*create cloud storage prior to leaving your country
*shortly before leaving your country, move your coin to a newly generated address, encrypt the private key via something that is complex but can be memorized.
*upload the encrypted seed to your cloud storage shortly before crossing the border
*destroy copies of files showing your association with bitcoin on your computer.
*cross the border
*create a new seed
*move your coin to the newly generated seed.