Traffic shaper based on link availability

Maybe the traffic shaper is not the solution. Maybe you are looking to prioritize other traffic, and in that case you can use DSCP to set a lower priority to the OneDrive traffic (per policy):

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Differentiated-Services-Code-Point-DSCP-making/ta-p/190923

Changing queue with DSCP marking to put "always-lower" priority on one type of traffic is one way doing traffic control. But it wouldn't provide a guaranteed bandwidth in high traffic situation because with FGT "scheduling" method until higher queues become empty lower queue packets can't go out.

In shaping-policies, you can specify applications like OneDrive (I currently see four types) and apply a set of shared-shapers (both directions) regardless the source/destination IPs, which you probably don't care much. You can set guaranteed (minimum), maximum bandwidth, and even DSCP values to control queuing if you want.

As warning in GUI says you have to have at least one application control profile applied to a policy in order to make applications in shaping-policies active.

Toshi