I'm using 'iiR5' to connote where the root of the 'ii' falls on the fifth string within the diatonic boxes I've memorized. The box 'r6 Mixolydian' is a scale shape I visualize, a 'box' which is equivalent to the Mixolydian mode where the root is on the sixth string. I know the 'boxes' for Ionian, Dorian, Phrygian, Mixolydian and Aeolian modes with a sixth-string root. I learned these boxes through the CAGED method.
Part of my practice is playing an arpeggio and finding a corresponding mode 'box'. As minor chords can either be the ii, iii or vi -- they correspond to different modes, and different 'anchors' on the diatonic boxes.
Another part of the practice is staying within a box and finding the ii and it's corresponding arpeggio. Then find the V and I.