Plain text is easy using an Execute an AppleScript action.
set theText to the clipboard as text
set theTitle to paragraph 1 of theText
set theNotebookName to "Default Notebook"
tell application "Evernote"
tell notebook theNotebookName
create note title theTitle with text theText
end tell
end tell
Styled text is less easy but possible.
There are several threads on the forum about Evernote worth reading - use search to find them.
At “Evernote ▹ Preferences ▹ Shortcuts ▹ Paste to Evernote” I have “⌃⌘v”. I have a very simple global KMacro that consists of two Actions: Copy, and Type “⌃⌘v”. This copies the current selection, opens Evernote’s Quick Note window, and pastes the copied selection into it. I click the button “Save to Evernote” and the note is saved, in the background, to Evernote (if Evernote is closed, it doesn’t even open), and the focus returns to the program in which I had made my selection. The title of the Note is the first line of the selected text. Styling is retained.
Evernote is, IME, fussy to work with; after my initial excitement got tempered by many small difficulties, I stopped using it regularly. But this still works for me.
It's VAGUELY POSSIBLE that they might add some JavaScript to the Electron app sometime in the future, but I'll be highly surprised.
If you want Evernote 10+ to be scriptable on the Mac then take everyone you know who uses it and start SCREAMING on the Evernote forums for that functionality.
I will not even install Evernote 10+ until I can't use v7.14.1 anymore.