That's very vague... Be specific about what changes you'd like to see, and make a case for Peter to spend the time, money, and resources necessary to make those changes – a case that affects hundreds of users – not just you.
While this is definitely an annoyance most Keyboard Maestro users don't have that many macros and don't see the problem.
I very much doubt @peternlewis will consider any form of auto-delete function – for duplicates or otherwise.
I would like to see import date amongst the available search strings.
That would help users keep track of items that were imported and not simply created.
But you don't really need to bother searching for something you just worked on. The Keyboard Maestro Editor has functions to rapidly get you back to your lost place:
I use Previous Edited and Next Edited all the time to jump back and forth between a couple of macros I'm working with – and to return to my place if I accidentally jumped out of the macro I'm working on for some reason.
You can click and hold the highlighted buttons in the editor here to produce a pop-up listing:
When I said added I meant from Finder. Imported. Next time I will write the word I meant lol.
I've tried searches and AppleScript, which work great for created and modified, but not imported as you suggested above. Navigating back would work in this specific case, but I would still like to see import date included.