How to find a keyboard shortcut association?

Sorry, that doesn't help - I would like to know which key is currently assigned to what, and not what is a default by Apple. I could have changed those long time ago, or it still could be a shortcut used by a 3rd party app - that's what I need to figure out.

A followup: I am now on a freshly installed new iMac with OS El Capitan, also on a newer Animate version, and still this shortcut is not giving me a break - same error sound. I do get it also in some other apps, some apps just don't do anything, and in Photoshop, when I try to assign this shortcut to any command, it says it's reserved by the System to cancel an operation!

and the most interesting - I used Cheat Sheet to list all the available shortcuts, and the Command + . is not listed anywhere, except the one I have set up manually in Animate, which doesn't work! 😠

Thank you

That's what I tried to understand, strange that it's not really listed anywhere. Although I do remember, that this shortcut did not have this issue until some recent updates of Yosemite or maybe it was in the previous OS , I can't remember now...