Case in point: I’d found that the ChipKIT Uno32 (a Microchip PIC32-based Arduino compatible) had one mounting hole slightly offset from a true Arduino. But an oval-shaped hole could accommodate both the true and derivative boards. Though I don’t use the Uno32 a whole lot, I still incorporate this same mounting hole set in any new design…the work is already done, there’s no reason to lock out those boards, and there’s a subset of users who will appreciate it.
Once a design is well-settled upon, it’s okay to discard this history. They’ll fill up your life otherwise.
Backup software like Time Machine isn’t suitable for this, since it’s based on regular time intervals, not immediate file changes. Some applications may support a version history…or the version control systems used in software development (e.g. Git) might be viable; I’ve not explored this yet as the sequential files have been sufficient to provide a basic “rewind” capability.
Sometimes a design can’t be keyed asymmetrically, but there are other ways to work around it. Case in point: the front flap on our Internet of Things Printer relies on two identical “hinge bumps” to pivot upward. It seems that about half the time, users install this part reversed…it’s still perfectly functional, but the stylized “@” symbol is flipped horizontally and many don’t recognize the mistake. In the second version of this kit, the fix is simply to use an image that doesn’t “read” one way or another: the language-centric @ sign was switched out for a cloud and makes sense either way.