Question: I'm wondering if it's possible to search for a certain line of a text using Xcode's Find & Replace feature, and fully delete the line so not even blank space is left over. Is this possible and if so how?

Answer: 
Copy the line you want to delete, including the newline character at the end of the line by triple-clicking on it (the selection should go all the way to the far right side of the editor pane). Perform a find and replace; paste the line into the the top field, and leave the replace field blank. Click Replace All.
On the latest Xcode you can just insert line break in the search field. Click on magnifying glass icon -> insert pattern -> Line Break

[![enter image description here](https://i.stack.imgur.com/OZvq2.gif)](https://i.stack.imgur.com/OZvq2.gif)