I don't have any direct experience with cartridge filters, but it looks like you could use that drain plug as a location to add a cut off valve and bleed off part of the flow. It should be a 1.5 inch NPT plug, Hayward makes a maintainable 1.5 inch valve with female threads on one end and male threads on the other that should easily screw into that hole. You can then get a roll up "blue" discharge hose that will connect to the other side. Or if you want something more durable, you can often find out of certification date fire hoses that have never been used from cabinet installations on ebay for $25-$40 which is the same ballpark price as the thin blue hoses (maybe a bit more), just beaware fire hose threaded connectors don't usually use standard pipe thread so you may need a $10 NPT to NST or NH thread adapter.
Ike
p.s. correction after looking at the parts diagram it looks like the plug is likely 1/2 or 3/4 inch, not sure if it is before or after the filter cartridge though, since it has an o-ring it is also likely parallel thread, still Hayward likely has a drain valve replacement for it, too many people have indoor mechanical rooms that require remote draining for them to make a filter that has to be drained directly.
