How do I deselect the Blade Edit Mode in DaVinci Resolve?
So you can just click Arrow button, or press "A". To select blade again, press "B".

Now that you know how to turn the mode on and off, you may want to learn a little more about what it is. The blade tool is very convenient thing to cut video instead of dragging by the end of footage.

I'd strongly recommend considering "Blade + select + delete" editing. It's working tool.

Now there are two ways to use interface in such editors: 


Point and click.
Short cuts.