Does Plesk support link aggregation/bonding?
Plesk was not tested with a link aggregation as the HA (High Availability) solution.
However, Plesk doesn't interact with a hardware or logical interfaces (like VLANs or bonds) but works directly with their IP addresses.
And in a case of link aggregation - upper layers communicate through the logical bond interface which has an IP address but eventually the active physical interface(s) communicate to lower layer 2. It also provides transparency to upper layers by hiding the actual interface.
Which means if bond interface works properly and IP address is not changed Plesk will keep working just like nothing was changed in the server configuration.