It appears impossible to get spare circuits to appear in Electrical circuit schedules.
For the next release of Revit, please make spare circuits added in Panel schedules to appear in a circuit schedule of the same panel. Currently the only work around is to create a dummy fixture with a load named "spare", (with multiple connectors) and connect multiple times to a panel (for each spare circuit required).
However when using Revit 2021 New circuiting naming parameter, load abbreviations and panel abbreviations can mess up the naming. A spare circuit should just appear with text saying "Spare" or "-" in the circuit naming, regardless of the makeup of the circuit naming parameter.
Please implement this as an alternative to using Panel schedules, as the later cannot be split across multiple sheets.
Thanks for listening.