Nano doesn't have a default keystroke for "match an end-of-sentence" character, though creating such a binding in .nanorc is trivial.
However, since what this typically means in practice is you'd either cut until the next period, or until the end of the line, in the absence of an "end of sentence" keybinding, my approach to this would simply be to either cut until the next period, or until the end of the line as required, which I believe is a wholly reasonable alternative.
The 7 keystrokes become very vim-competitive when you realise that d)Gp actually fucks up in the typical scenario, since usually what you want is NOT to paste after the first character of the last line, but actually in a new line below the last one. Which means you don't actually just do `p`, but something like `o ESC p` instead.