Strip trailing whitespace on Save with …callbacks!
Open the bundle editor (⌃⌥⌘B) and open “Text” → “Menu Actions” → “Converting / Stripping” → “Remove Trailing Spaces in Document / Selection”.
Then in the drawer put callback.document.export in Semantic Class and Document / Replace Document as Input / Output.
Hooray! From now on each time you’ll save a document all trailing space will be stripped!