But there is another pitch correction. Not in edit pane, but smart controls-plugins-popup menu. One thing there is a pitch shifter, other are compressor etc. What about them, how to use them.. ? Do they have different effect than edit pane pitch correction? Do you have any video.. ?

Plug-ins are audio processors that can do many different kinds of processing, from EQ [tone control] to compression [dynamics control] to effects [chorus, echo, reverb, etc]. It's a more advanced topic, but when you get to that point if you want to learn all about the various processors and effects that are used in recording and mixing you could check out this Audiopedia course: https://www.macprovideo.com/course/audiopedia-mixing-mastering?afid=E470KLQ7r9 This is not specific to GarageBand, but these plug-ins/processors are available in pretty much all DAWs.

OK, thanks for the course! You write, plug-ins are more advanced. Am I understand rightly that firstly I can use editor pane pitch correction and only after that it has sense to use a smart control pitch correction? Right?

AFAICT, it seems like the Pitch Correction plug-in in the GarageBand Smart Control pane is automatically inserted when you perform pitch correction in the Editor pane..? It opens up a mostly blank plug-in window with no controls, only a message that says "This plug-in provides compatibility for projects created in GarageBand for iOS". I couldn't find any mention of it in the Apple GarageBand documentation, or anywhere else for that matter.* It doesn't seem to do anything on its own, so I would just ignore it -- if you want to do pitch correction in GarageBand, stick to the Pitch Correction slider in the Editor pane. * There's a Pitch Correction plug-in in Logic [same name], but that is a completely separate real-time pitch corrector, like Auto-Tune, with its own set of controls. The one in GarageBand appears tp be something completely different, AFAICT.

OK. About the button which turns flexing on or off. You see on the video, that button is active and also pitch correction is seen. As it meant to be. Then I inactivate that button, pitch correction is still there. I understand if I turn flex off ( by help that button ), then pitch correction possibility should go away also... ? OK, I activated button again and tried to remove a selection of enable flex but then all pitch correction disappeared at all. Why? After that I activated button again, but not pitch correction appearing. Then I inactivated button and with that pitch correction disappeared still with selected enable flex. ( Like I turn off flexing and then flexing opportunity - pitch correction - appeared ). With that inactivated button I tried to remove enable flex, again pitch correction disappears. Again button activated (flex on), no pitch correction. After that, again button inactivated (flex off), again pitch correction appearing. Why the button works vice versa and why I can't get rid of the enable flex selection.. ? https://youtu.be/sUrPVNYYkdI

Apparently, when you first turn the Flex button on it also checks the Enable Flex checkbox and enables the Flex feature, but after that the Flex button only turns the Flex waveform display on or off, not the Flex feature itself. Once it's enabled, it seems that clicking the Enable Flex checkbox disables Flex, and hides the waveform Flex view and turns off the Flex button. Not the most logical system, but that seems to be how it works, at least here. Sometimes when you're in the Region view and you enable or disable Flex it switches to the Tracks view controls, but the Track tab does not light up as it should -- a graphic bug, apparently. If that happens you can simply click the Region tab to restore the Region controls. And again, that's separate from Pitch Correction -- pitch correction is not controlled by the Flex button, only by the Pitch Correction slider. Here, the Pitch Correction slider and the buttons below (under the Track tab) and the Time Quantize controls (under the Region tab) are always visible (in their respective tabs, except for the aforementioned graphics bug).

OK. I enclose a video, you can see that pitch correction is also under track view. And in region view. So, what it means - I can pitch correcting the whole track or only a region, isn't.. ? And in track view, I can get rid of the enable flex checkbox choice... https://youtu.be/zzhJh7D4zUg

As I said in the previous post, it seems that sometimes when you're in the Region view and you enable or disable Flex it switches to the Track view controls, but the Track tab does not light up as it should -- a graphic bug, apparently. If that happens you can simply click the Region tab to restore the Region controls, and then switch back and forth between Track and Region functions normally after that. Despite this occasional graphic bug, Pitch Correction is a Track function -- it's on of off for all Regions in the Track. And, again, don't forget, in GB Flex and Pitch Correction are two different functions.

Well, if pitch correction is a track function, then I don't need to use region tab and flex button to get visible pitch correction slider, right? Not at all.. ? Or why is then pitch correction slider is under region tab and appears by clicking to the flex button.. ? What is the sense of that local pitch correction there.. ?

That's correct, you don't need to use the Region tab or the Flex button to access the Pitch Correction slider. As I said, the Pitch Correction slider should appear only under the Track tab, but there's apparently a graphic bug -- a mistake in the code -- that sometimes seems to make it appear under the Region tab. If you ever see the Pitch Correction slider under the Region tab, just switch to the Track tab, and ignore the bug. There is no sense to it, it's a bug, a mistake in the GB code -- maybe Apple will fix it someday..