Oregon Covid-19 Pandemic (DR-4499-OR) is not in the dropdown list to answer "Which disaster affected You in 2020?" Is it safe to leave this blank?

Actually you are trying to enter this into the wrong section of the return. Here are the correct steps.

1. Go to federal>wages and income>all income
2. Retirement plans and Social Security>show more 
3. Ira (401K), pension plan Withdrawals(1099R) Start
4. Here you will enter your 1099R.  After entry:
5. In the first screen where it asks,  Do any of these situations apply to you? Here say none apply to me. You will not enter the Coronavirus information in this screen so this is safe to be left blank.
6. Continue through the section until you arrive at the 1099R summary page. Select continue at the bottom.
7. Have you ever taken a disaster distribution before 2021? Here you will say yes.
8. Next you will need to enter information from your 8915-E that was included in your 2020 tax return. This will report your 1/3 payment that is required to be reported this year.

I appreciate the information you're giving me, but this is exactly what I had done in the initial go-through. It wasn't until I revisited the section that the question popped up, and it showed up in-between questions I'd already answered before. 
From what I gather though, you're telling me it is safe to ignore this question and move on, though?

Yes, it should be safe to move on but let us know if it doesn't. 

@piccolo113