I've just discovered that the OCR action isn't atomic. That is, if I have two separate macros running simultaneously and each macro performs an OCR action, the variables in the other macros can end up storing the text from the other macro! I don't think this is desired behaviour. Probably a bug. It has taken me days to figure out that this is the probable cause of my problems (if I was smarter I would have realized it faster.) It's difficult so submit code that will illustrate this, I'll just leave it to Peter to opine on whether my theory could possibly be correct. If this is not fixable then at least the OCR action documentation should explain the issue and advise on reliable workarounds (semaphores might work, but I didn't test that yet.)
On a related matter, it would be really nice if I could lower the priority of the OCR action. That action bogs down the responsiveness of the system. I can use the macOS "nice" command to lower the priority of my command-line-based OCR software, but I can't do it with the built-in KM OCR action. To me that's a missing feature. In general when I use OCR I'm not in a rush and I would like to lower the priority of the OCR action. (In fact a similar feature might be handy on any other actions that require heavy CPU processing, perhaps the Find Image action.)
Also I've noticed that when I try to use the OCR action on a blank area, I tend to get this error: "Warning: Invalid resolution 0 dpi. Using 70 instead." (I'm using a 5K iMac monitor.) What is the recommended way to deal with this error? This probably should also be in the OCR action documentation.
But I must say I love the new OCR action. It's pretty fast (though not as fast as the miraculous Find Image action) and usually pretty accurate. It does however glitch badly on about 0.1% of the words that I scan. And when I say glitch I mean totally bungle the word even when it gets the words around it 100% correct. For example, if I was trying to read a sentence, I occasionally get a glitch like this: "Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall, all the King's eaieoaeiaoaei and all the King's men couldn't put Humpty together again." Repeated calls to the OCR action result in the same error. But if I move the image to another part of the screen there's a chance that the OCR action will return the correct words, but generally that trick doesn't help.
I have other things to say about the nice new OCR action, but I'll save them for another time. I decided to post this now because I think this information may help users to use the new OCR action.