You need to hold the Option key down while you click on the Go menu on the top of the screen. The drop-down list will then show Library as one of the options.
Rafael, I did. I held it down the entire time. It still does not show
Odd. Try this:
Make sure the Finder window is active.
Without pressing the Option key, click and hold the Go tab on the top of the screen, so you see the drop-down list.
Without letting go of the mouse, press the Option key.
Do you see any changes on the drop-down list?
Try making hidden folders and files visible temporarily following the steps described here Quickly Show/Hide Hidden Files on Mac OS X Mavericks & Yosemite | Ian Lunn - Front End Developer, it applies to Mavericks but I think is also valid for Yosemite (but not 100% sure). Please don't use a external drive when hidden folders and files are visible as there might be a bug with LR5.7.1 on Yosemite when they are visible (not fully sure).
When you are done with the preferences, make hidden folders and files invisible again.
Thank you so much Rafael!!! clicking go and holding it and then pressing the option key did the trick - yeah! Now I can reset the LR preferences and hopefully my 'edit-in' will work again - opening/loading files into PS from LR. Fingers crossed Thanks again. Also thank you to Modesto Vega for the other suggestion!
You are welcome!