I'm a content author using Sitecore 9 (maybe 9.1?) and when I went to preview a page in the content editor area I expanded the content editor, which hid the content tree. I am unable to get the content tree back and I do have the content tree selected in View and within the view tab in application options.
Just move your mouse to the left side of the screen until you see a small arrow there (it may look a bit different in other browsers).
Then click and drag to the right.
I have also tried that, it doesn't move.– ShannonJul 11, 2019 at 13:30
It does. Just make sure you place your mouse at the "height" of content tree, not at the height of the tabs bar. See on my screenshot - it's at the level of item name ("Home"). If you try at the level of the "Content" tab, it won't work. Jul 11, 2019 at 13:35
You may also try another browser and expand content tree there then switch back to the original browser and log out and log in again. Jul 11, 2019 at 14:30
Thank you Marek, you were right about the specific height of where to drag. It worked!– ShannonJul 12, 2019 at 15:10
@Shannon I'm glad it worked. If you find this answer useful, you should mark it as correct. Upvoting is also encouraged Jul 12, 2019 at 17:36