This might be obvious, but I thought I’d share how I used a Select List Column to automatically trigger a True value in a Check Box Column AND leave the Check Box Column still in a manual state (aka untethered to the selection column list) when a form is submitted.
In the editing section of the checkbox column, I used the Contains() formula referencing the selection list in “default value” section. Now, I can hide the selection list and the my team can use the checkboxes to manage each athlete’s event after a parent submits a registration form.
Previously, I displayed the checkboxes in the form and used an image to provide instructions. It worked well, but the ui/ux was inconsistent with the selection list views and I could not limit the selections a user could select (See Image Below).
Why would I need this?
Checkboxes are quicker for users to identify and use. I work with children and they change their minds frequently, so being able to quickly click a button makes thing easier than having to manage a drop down and list. I also push, pull and filter a lot of data across documents and need the actions to happen pretty quickly, the true/false Boolean keeps my docs a little lighter compared to scanning when my data sets get large. I find that, checkboxes are also a better option for ipad/tablet users without having to create a column for a button or other work around.
This is more a ux/ui detail, but I really appreciate the small work arounds that can improve my automations. 
Hopefully this can help others!
-Brittany