How to get rid of this thing?
Cmd+Q. Of course, that will close the entire program. It's part of the interface and you can't get rid of it.
Really? After multipe ID crashes i had to reinstall CC, then it appeared. Its quite annoying, cant find a suitable place.
Sorry, only caught part of it on screen. You have the application frame turned off and I don't have a Mac here to see if that's the issue. Try turning it on.
Turning on application frame is not helpful – years of drag'n drop workhabits on Mac is lost with one window system.
I think it is bug that this little toolbar has no close button (or something equivalent in menus)
It's part of the title bar. I didn't say leave it on. But if you don't want to do any troubleshooting to see if there's a bug of some sort I've got nothing else.
I'm using windows, however, have you tried changing the workspace (Windows >> Workspace >>>) try a different workspace layout. Hope it works out
That is the InDesign Title Bar. It can't be turned off but you have undocked it, which is why it is now in the way. Interestingly, you cannot re-dock it by just resetting the workspace. You will need to grab the far left edge which is a slightly darker gray in your screen shot and then drag it up towards the Menu Bar. When you see a blue horizontal line under the Menu Bar you can release the mouse and it will go back to its normal position.
You can also reset preferences, but that seems like overkill.