I did dual enrollment in 11th grade, but none of those courses are UC Transferable. I should report them in the "other coursework", but when I try to move on with the "College Courses taken in High School" section, I have to list at least one course

Colleges & Universities University of California - GENERAL
10

The UC Counselor conference stated all DE classes should be reported since you will be required to submit a transcript upon enrolling.

Edited: Based on a similar situation last year, you can just report them under Other Coursework as noted by @lkg4answers.

Please report all grades you received for all academic courses you enrolled in, including withdrawals, incompletes and courses you may have repeated at a later date. Do not list athletic courses or courses that are under 3 units (courses under 3 units do not satisfy the UC “a-g” subject area requirements).

So my mistake in stating you need to report them under the College and the UC conference information did not specifically address 1 and 2 unit courses nor the link I gave you.