No more ruler in the Editor window from Toad 12.7. In version 12.6 or less, the position indicator was shown at the top of the editor but has disappeared in 12.7

WORKAROUND 1:
In the meantime if you look to the lower-left of the editor (in the status bar) you'll see the same information that was visible in the ruler. It's just not as easy to visualize from a quick glance.

WORKAROUND 2: Avoid long lines that exceed a certain length.
Look in the status bar or use one of the options for showing long lines.
1) Go through View | Toad Options | Editor | Display option.
2) On the groupbox Edge, set the dropdown to:
Line: shows a permanent, vertical line, at the column position
Background: shows nothing until a line exceeds column position and then, the background color is changed to highlight the excess.
3) Then, select Editor | Font and Styling option. You can change the color of the line and background. See the "Edge" style on the Global styling tab.
NOTE:
If you want the ruler to come back, please go to Idea Pond (https://www.toadworld.com/products/toad-for-oracle/i/editor) and enter your request if it is not already there.
Idea Pond is a site where you can tell the development team what you want, and tell us how important it is by submitting, voting, and commenting on ideas. Just sign in and submit your idea there.