With regard to the standard Whisk in Waltz as standardised in Howard:

What is the directional course of movement in relation to the room for the lady's LF in order to end diag back on step 2 ? Over the first part of step 2, does the LF move backwards along the same line as step 1, or is the direction changing during this period ? Until what point does the R heel stay down in accord with the NFR on 1 ?

Thank you in anticipation.

No directional instruction is given, but I would say that the LF foot should commence to move DW (ie as RF on step one) so that the foot comes under its own hip, and once the feet are more-or-less parallel, the track of the foot should curve to the finished position diagonally back, pointing DC, rather like the shape of a hockey stick.

Step two is a backward, rather than side step, so the normal inside turn NFR rule of releasing the heel as weight is taken on step two would not apply; but in fact this is effectively what is required, although no specific note is given. However, if you look at the man's R&F on the Back Whisk, you will see that Howard provides a note that the H of the LF is released when crossing LF behind RF. Lady uses the same R&F in the Whisk, where it is she who makes the backward movement.