As options guidelines can be enabled and disabled. There is no option to add guidelines neither help about it.
Draw.io – How to Add Guidelines
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Related Solutions
For how to share a draw.io diagram with another user generally, see the FAQ entry on the subject.
Repeating the current content:
You can share a draw.io diagram stored on one of the cloud storage options with another user using the built-in sharing functionality of that platform, https://drive.google.com in the case of Google Drive, https://www.dropbox.com/home in the case of Dropbox and https://onedrive.live.com in the case of OneDrive.
Google Drive also allows the option to share within the application itself, using the blue "share" button top right in the app.
Note that only Google Drive supports real-time collaboration between users, Dropbox and OneDrive are last write wins.
If you are not using a cloud storage option and are saving the diagrams locally, you must manage your diagrams yourself, we do not have copies of the diagrams and cannot offer sharing functionality.
Next to the "Grid" checkbox on the Diagram menu, there's a numerical value. That's the size of the grid, which you can increase and decrease.
Visual:
Best Answer
Guidelines are there to help you align elements to each other.
Try the following: On an empty canvas add two boxes, and change the size of one of the boxes. Then start dragging the smaller box around the larger box. Now you'll see that the guidelines will appear when the edges of the boxes align, or when the center of the boxes align.
This can be very helpful when you have multiple boxes and you want to order them properly. You can then align them using the guidelines.