TLDR: I suggest that constant combinators be able to have their settings adjusted from the map (global range)
WhatTrain stations currently are configurable globally. The player can select them from the map screen which brings up the station's settings menu. I suggest also extending this behavior to constant combinators.
WhyCombinator circuits serve as a means for the player to creatively implement automation logic on elements of their factory. The constant combinator often operates as a form of parameterization of that logic. However, the power of the circuit network is dampened by the fact that the player has to be next to a constant combinator in order to change its settings. This can already be done in a hacky way using a destruction planner, and then dropping a new blueprint down, so making constant combinators globally-accessible streamlines what is already in the player's capacity to do.
Giving global access to constant combinators meshes well with other global factory control features. Trains currently allow global access to their settings. This rewards the player for planning good rail networks and helps minimize the amount of tedious running around necessary to manage them. Blueprint's can also be stamped down globally, rewarding preparation and forethought from the player. Similarly, a globally-configurable constant combinator would reward players that devise clever circuits to manage their factory operations.
A concrete example:
I have a blueprint for a construction train depot. It has logistics storage chests and a roboport. A constant combinator describes to a circuit what items to unload into the storage chests in order to build (I don't want to unload miners if I'm building circuit assembly, for example.) From the map screen I can deploy the blueprint. From the map screen I can send my train to the station. However, my character has to walk/drive to the station in order to configure the constant combinator to request the right items.