Another (real life) example: I have a duo for violin and piano, in seven movements. In two of the movements the violinist, instead of playing violin, is supposed to play the Primo part of a piano four hands setting. There are two Layouts, the playing score and the part for the violinist. The playing score does contain all materials in the common order. The violin part, however, comes in two sections. First, there is a usual part for all the movements with participation of the violin. The movements where the violinist plays piano are left out since they are played from the playing score (at the piano). They are, however, still included in the violin part, in the additional second section. This is necessary so that the violinist can practice the Primo part.
I: violin and piano
II: violin solo
III: piano four hands
IV: piano four hands
V: violin and piano
VI: violin solo
VII: violin and piano
Playing score, order of movements:
I, ii*, III, IV, V, vi*, VII
Violin part, order of movements:
I, II, V, VI, VII | iii*, iv*
*movements given in small Roman numbers are not played from the Layout
I was able to achieve the violin part by using two unlinked frame chains and filtering out the unneeded Flows. Having the ability to set up very deliberately the order of frames that the music flows through would be a bit less hassle here (it may come with other complications, though), but this filtering approach sure is fair enough – and look at me talking as if having something like frames at last is just something to be taken for granted.
Currently though, this method comes with another problem that probably also applies to Robert’s example: it is not possible to only have unlinked frame chains in a Layout (which is what you need to divide the Flows assigned to one Layout into separate sets). The moment the last Master Page frame is turned into an unlinked frame, a new page will be added to the Layout with a new Master Page frame.