we got an assignment in class to create a Sibelius score from PDF file. Now I was wondering how I can create a pickup bar only for the "Continuo" instrument. And how it's possible to shift the barline brackets after the pickup bar.
Add a new bar before the first bar of your completed score. Select it and untick all the boxes in the Bars pane of the Inspector (Brackets, Initial clef, barline, key signature).
For each staff that you wish no incipit to be shown, select the first bar and make an instrument change to a 'No lines (hidden)' instrument for that bar only. For each staff you wish to show an incipit, change the rest type in that first bar to 0, or simply hide the rest.
Select the barline between bars 1 & 2 and drag it left until it's a suitable size for the incipits. Then choose Create>Barline>Invisible and apply it to that barline.
Select the second bar (the former first bar) and make the Gap before bar (also in the Bars pane of the Inspector) -0.06. If necessary, insert a bar number change to make this bar 1 again.
Use cue-size symbols to insert the incipit clefs and/or time sigs and/or notes.
I think that's all. Beware that braces (not brackets or sub-brackets) will look terrible if you run the incipit staff directly into the main one. In that case use a positive Gap before bar, and everything else will still work.
(From a post by Jeremy Hughes in the official Sibelius forum.)