Is there a way to filter what lines show up on a chart from the outside like you can date and other values?
There is a beta for page filters that's currently in BETA. https://knowledge.domo.com/Optimize/Filtering_Data/Applying_Page-Level_Filters_(with_Filter_Views)_(... which allows you to apply different filters to an entire page / dashboard. Talk to your CSM to get enrolled in the beta for this if you're interested.
The other option is to create Filter Cards based on the same dataset which allows the user to interact with on the page. When they select elements from the filter card it will filter the rest of the dashboard.
They're outlined here: https://knowledge.domo.com/Welcome/Available_Chart_Types/Available_Filter_Charts
Selecting specific values from the filter chart should then only show those values in the other charts on the dashboard.