Multiple diabolos can be juggled on a single string, usually in a circular pattern, by either continually throwing them high by lifting and pulling the sticks apart, or pushing with one stick when a diabolo gets near it so that the string pushes it across to the other side of the string, going over the other diabolos. This second method results in a lower pattern with more than one diabolo on the string at once, called a "shuffle", which may be easier for 2 or 3 diabolos but is more difficult for higher numbers.
Ofek Shilton has juggled 5 diabolos high for 54 catches (video), and Robin Spinelli has done 5 low for 13 catches (video). Tony Frebourg and Guillaume Karpowicz have passed 8 diabolos between two strings for 10 caught passes (video).
Diabolos can be juggled in siteswap patterns, where a 0 is a pause with an empty string (with time to do a 360 or jump rope with the string), a 1 is a pause with a diabolo on the string (with time to do a sun), and 2, 3, 4 etc. are increasingly high throws.