Change to unusual Time signatures mid-song.

I have to change time signature in the middle of the song, to 7/4.

Since 7/4 is not represented in the palette... how to get it there?
In "Time Signature Properties I can only change the appearance so it says "7/4", but it doesn't actually make it 7/4.
How do I get to the actual value to change it? Song starts with 7/4 and that only worked because I could choose that while making the project. But now? I use a mac.