14.42The diminished chord's real secret

It often looks complex on paper, but at the keyboard ask:

Which note is the destination?

Then:

Can I put a diminished seventh chord one semitone below it?

Destination D:

C♯°7 → D

Destination G:

F♯°7 → G

Destination Am:

G♯°7 → Am

That gives you an immediately usable tool.