add instrument middle of piece.
i know that there is solution for hidin empty staff. But problem is when compose for orchestra there have to be div. for example 2 flute same staff flute I and flute II is another staff. it's mean 3 staff for flutes. if go on like this all for orchestra i have to open 36 staff. after i write all then hide staff. it's very hard to write. may be after section break we can make new insturmantion. also we need that between movments.