Oh yeah, now you mention it I can see it in the manual. Unfortunately there’s no explanation as to what it does. …though it seems I’ve been here before [two years ago]
Ecodan pump speed settings - #31 by Timbones
the manual for FTC6 mentions something called “Water flow control” under Operational settings. I’m not brave enough to try it…
A later post Ecodan pump speed settings - #33 by Vinny speculates that this feature is expanded on within newer controllers. See whole topic for more about the pump settings.