There is no Scheduler option to signify that you intend to use the Single Rider Line. Reason being is that the single rider line wait times are not at all consistent. Sometimes your a big winner and sometimes you might as well have been in the standby line, which make predictions very difficult. Without a high level of confidence in the result, it isn’t a good fit as an option.
You could use the Lightning Lane wait time as an approximation, and you have already seen this in action in your recent LL Premier topic as answered by @Jeff_AZ Premiere Pass - #12 by Jeff_AZ (see “round 2 good”). In short, you do not turn on a LL option, but do configure a return window that brackets the arrival time of the single rider attraction. Follow Jeff’s setup closely.
FYI .. In regards to using LL Premier when there are multiple instances of an attraction, I have some additional information I can pass along if you are still interested