It's in the Subtext- Write better dialogue: a workbook for writers on how to write great dialogue (The Writers Inventory)

Master Subtext in Your Writing

Did you start writing your book but get stuck on the dialogue? It's OK—it happens too often to everyone! just try to slow down and analyze the talk and the silent moments between your characters.
This workbook is a personal tool for you as a writer to exercise the key techniques for writing great dialogue. It answers many questions, such as "When should your characters speak directly?" and " When should they hint at something deeper?"
What awaits you inside? plenty of exercise! you'll learn how to:

• Enhance dialogue with layered subtext.
• Use silence and actions to reveal hidden meaning.
• Show character emotions and motivations subtly.
• Apply subtext effectively across genres.
• Avoid overly obvious or flat dialogue.
  The book also includes bonus pages- experimenting and brainstorming pages, and a place for notes!

Write nuanced dialogue, develop dynamic characters, and create stories that resonate with readers.