"Edit local file and upload it" option ?

[bigstar]

did you configure FlashFXP to use notepad++ to edit the file or are you starting notepad++ in some other way?

From within FlashFXP on the main menu, Options > File Associations

Add a new file association for example

File Mask
*.txt

Open With
\path\to\notepad

check the two options
[x] view
[x] edit

finally click the save button.