When I checked out if there is a way to force the intercept to 0 or some other constant value, it's not doable from the tool configurations.
So manually we can have "0" intercept in linear regression this way (edit the macro's R tool)
cars.lm <- lm(dist ~ speed, data = cars)
cars.lm2 <- lm(dist ~ 0 + speed, data = cars)
summary(cars.lm)
So a minor addition of a tickbox will solve that and make that linear regression tool more flexible i guess...
Best...