Is shell History a text list or is it a workflow automation/virtual environment session eg Vagrant ?
It is first and foremost a command that lists the history whose output you can process by Shell tools. The implementation is that of an exec-style doubly linked list. There are currently no other tools around the history.
Could the soft-links work for example in a large project with all same header files all using soft-link to *one*, so
change *any* header (.h) changes all of them? - that would be nice to have.
Softlinks are soft-links, you can use them as you like.
Does 'replacing ROM components' mean replacing class/data structures, or like apt-get ?
AmigaOs doesn't have dpkgs, it has modules. What L:System-Startup (or its ROM-version) does is that it replaces such modules.
This could mean UI elements can be updated with new features like auto crash reporting, UI dependency check/download
and also automated UI regression testing.
Well, for that you don't need System-startup. You can replace intuition boopsis right away without requiring a rom patch. But yes, intuition and gadtools are "loadable moduldes" system-startup can update from disk if it finds a newer version.
The most difficult part of programming Amiga API is figuring out how to interact safely with other libraries
Actually, the APIs are documented in the autodocs. Sometimes not as complete as they should, though.
At times I select a file and hit DEL expecting it to just delete. lol.
I suppose you mean on the workbench. Well, workbench is disk-based to begin with.