Obviously it depends on what kind of piece you are working with, but the work-around in my case has been a simpler method: I used triplets or other variants and then hid the brackets/numbers. Afterwards I'll add the time signatures in by text. It's one solution.
Thanks a lot from Italy... But working with big orchestra you have to manage the entire score layout, and more, soloists can be really hard work... but, at least it is a good starting point!
This is an excellent question. This is another special circumstance issue that Sibelius really struggles with. There is no automatic way to do this - you have to manually play with objects and the hide/show function to make it work. What a great idea for a new video - stay tuned!