All edit commands except Word Wrap affect whichever composition control is currently active (i.e. if the cursor is in the Subject field, the edit options will affect the text in the Subject field). Word Wrap only applies to the main body text.
Undo
Cut
Copy
Paste
Paste Unformatted
Delete
Add External Quotation
Add Quotation
Remove Quotation
Select All
Delete Line
ROT13
Word Wrap
Lock Max Window Width
Edit Header Part