I've got this working, but it takes about 4 hours to run because it's built so inefficiently.
Basically - I have a SharePoint calendar with the full company's PTO for the next 6 months (Calendar A). I need to sync it with a separate calendar that only has about 30 employees in it (Calendar B).
My current process is to get items from both calendars, delete everything in Calendar B, then do a nested "apply to each" - so each item from Calendar A is checked against an array of Employee IDs to see if they match. If yes, then I rebuild Calendar B from scratch.
It would clearly be a better solution to filter Calendar A by the array of IDs before running the Apply to each loops, but I can't figure out how to do that! Can I use the Filter Array action? If so, how?