The point is that in the route section of the web UI, you can define a route to an existing gateway or to a predefined "Null4" or "Null6" gateway.
The way the route is created seems to be bound by using these specific entries and they use the B (blackhole) flag, you can see this results in "USB" flags for the route.
Since you cannot set the "Reject" flag for a self-defined gateway either, I do not see any way to to this via the web UI. So your are left with either a feature request on Github or by creating a specific pf entry by other means than the web UI.
The way the route is created seems to be bound by using these specific entries and they use the B (blackhole) flag, you can see this results in "USB" flags for the route.
Since you cannot set the "Reject" flag for a self-defined gateway either, I do not see any way to to this via the web UI. So your are left with either a feature request on Github or by creating a specific pf entry by other means than the web UI.
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