After our discussion, we'll leave this PR open for now. Requiring a "single actor" seems like a bad idea, and it's pretty tricky to actually enforce, which only reinforce the impression of it being a bad idea (see this message).
One interesting solution would be to move OpenDRIVE loading to a subsystem, that would then be accessible to everyone (not requiring tools/actors to have a reference to the ODR actor/world setting). That way, World Settings and OpenDRIVE actors could even co-exist (as simple gateway to the subsystem), with the subsystem enforcing the "only one" rule.
After our discussion, we'll leave this PR open for now. Requiring a "single actor" seems like a bad idea, and it's pretty tricky to actually enforce, which only reinforce the impression of it being a bad idea (see this message).
One interesting solution would be to move OpenDRIVE loading to a subsystem, that would then be accessible to everyone (not requiring tools/actors to have a reference to the ODR actor/world setting). That way, World Settings and OpenDRIVE actors could even co-exist (as simple gateway to the subsystem), with the subsystem enforcing the "only one" rule.
Also, related to subsystems: https://github.com/aquanox/SubsystemBrowserPlugin