Legitimately curious, how would you implement a “secure” scratch file functionality? Or is it just that the whole notion of scratch files is insecure?
The great thing about Textadept’s extensibility (and use of Lua specifically) is that it’s easy to pull in other Lua modules to add functionality. I don’t think it would be much work to modify the scratch file extension to prompt you for an encryption key on startup and then run the scratch files through libsodium (via luasodium) if you want to have your cake (scratch files) and eat it (some cursory level of security).
I use Joplin, which is a cross-platform FOSS notes app featuring E2EE. It's not a perfect solution and not much of a text editor, but it's the right direction.
Everything else is explicitly saved (without secrets) or just an ephemeral buffer in Neovim.
The great thing about Textadept’s extensibility (and use of Lua specifically) is that it’s easy to pull in other Lua modules to add functionality. I don’t think it would be much work to modify the scratch file extension to prompt you for an encryption key on startup and then run the scratch files through libsodium (via luasodium) if you want to have your cake (scratch files) and eat it (some cursory level of security).