Progression templates and keys

The progression templates (12-bar blues, 8-bar, minor blues, I-IV-V, '50s, pop-rock, bluegrass…) are written in degrees (I, IV, V) and the Key turns them into real chords: 12-bar blues in A = A7, D7, E7; in E = E7, A7, B7. Replace chords clears the bars of the section and puts the progression in, Append adds it after them. Neither one transposes: to move a song you already wrote there is Transpose (Song ▸ Advanced).

Root ≠ key: the root is the note a chord is built on (A in A7, D in D7); the key is the "home" of the whole song. The 12-bar blues in A (A7 A7 A7 A7 | D7 D7 A7 A7 | E7 D7 A7 E7) has three roots, A, D and E, but only one key: A, because it revolves around A7 and ends there. Changing a chord changes a root; changing the key of the template changes the whole progression.