• negative numbers in operator expressions like max_speed * -0.2
• encoded value expressions like <ev>.ordinal() and edge.getDistance() (both numeric)
• some math functions like Math.abs/sqrt
• boolean encoded value-like expressions like edge.getName().contains("xyz")

See here what is allowed on the server side: https://github.com/graphhopper/graphhopper/blob/2140131ec079e21b7e7f05865a3b77913b0d9acc/core/src/main/java/com/graphhopper/routing/weighting/custom/ConditionalExpressionVisitor.java#L41-L42

It would be nice to have a negation alternative to xy == false, i.e. !xy.

Plus support for backward_xy.

For example pressing Ctrl+Space with the cursor placed behind "if": we do not get any suggestions. We need to type " first to make it work. Previously it was possible to use boolean true/false here (without "). Maybe that's why. But this is no longer allowed anyway. Same thing for operator values where we used to allow numbers like 100 instead of strings like "100". So we probably do not get suggestions when the cursor is placed behind "limit_to": for the same reasons.

I tested the RoadsTagParser with the RHS expression and used something like

{
  "speed": [{
          "if": "true",
          "limit_to": "small_truck_average_speed"
        }, {        
          "else_if": "small_truck_access==false && something",
          "multiply_by": "0"
        }, { ... }
  ]
}

as the custom_model but the request failed with

You requested the details
[road_class, small_truck_access, truck_access, average_speed, distance, time] but we could only find
[road_class, small_truck_access, average_speed, distance, time]

Probably the RHS stuff is unrelated and the problem is that we do no longer contain the $ in these encoded value? Before it was small_truck$average_speed and small_truck$access.

In production I will include a hack so that I can continue using it for this special case :) (so test this only on a local instance please )