I have to chime in here. I'm a brand new KBM user and this was driving me crazy as I am in the middle of creating my second macro and I wanted to RECORD using the Ctrl+Tab keystroke to switch tabs in Chrome.
Thanks to peternlewis's answer, I was able to change the default to something that didn't interfere with a keystroke that I use a LOT.
I particularly want to applaud joelparkerhenderson's suggestion of developing a a "just-in-time coach" as a user interface for onboarding new users. While not trivial, it's also does not appear to be prohibitively difficult to implement and would be a great complement to the feature of warning you if you define a trigger that is already in use, which is another form of "just-in-time coach".
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The Forum is asking me if I want to bump this old topic. I'm doing that specifically because someone mentioned that they can't remember anyone ever having this problem before. Here's hoping that he and others will remember that this is indeed a problem for new users, as evidenced by all the others who have added their voices to this thread, year after year.