Instrument Numbers

Hello,
as I am working on the layout of my scores at the moment, I was wondering if someone could help me with my biggest issue until now. How do I properly give staves for instruments numbers? Let's say, we want to have two flute staves seperately of each other in the score. I am so far with this: Creating a split stave to have the instrument name "Flute" between the two lines of the stave - but - how do I put numbers like 1 and 2 right in front of the staves of each flute? I have attached a photo of a score that shows how it should look. There are some ways to achieve to have certain numbers in front of the staves but these are dragging and dropping and making use of the arrow keys to align it...it just doesn't feel right. Does someone have an idea?