Thanks @AlexanderFillbrunn! I just spent some time learning a bit more about flow variables, and actually ended up creating some workflow and flow variables, as described in this video (Creation and usage of Flow Variables in a KNIME workflow). Also, I used the String Manipulation (Variable) node to configure the file paths.
I finally feel like I have a basic understanding of flow variables! I knew it would be powerful once I got there. I’m super excited to use them more on my future workflows now! Thanks for all your help with KNIME. I’m quickly becoming an advocate!