Bm7 to A
How to transition from a Bm7 chord to an A chord.
The Bm7 → A transition is the same vi7 → V move in the key of D.
Chord shapes
Play the Bm7 chord in an A shape, and transition to a full A chord. Keep your second finger in place, slide your third finger back to the second fret, and move your first finger from the A string to the D string.
Bm7Basically D/B
AFull
Anchor fingers: finger 2 on G string (fret 2)