How to supplement an existing plan with additional workouts

This is my first post and I’m new to TR as well. I live in the Southeast and have the luxury of training outside year round within reason. However, when it rains every day of the week I’m confined to my garage and the trainer. I’m 3 weeks in on Base Phase I, Sweet Spot Base, Low Volume 1. I chose Low Volume b/c I typically ride at least 3 days a week outside for a full 6 rides per week. However, on weeks when I can’t get outside I would like to add workouts to my plan for that week. Is there a ‘right-click’ option to supplement a plan with additional workouts? Or what is the best option for adding workouts?

I asked a similar question a couple of days ago, here’s the thread with some tips: