Thank you for your response. I do appreciate you taking the time to consider my request.

That is unfortunate. However, I have devised a somewhat rudimentary workaround. It works as follows:
- Enter manual "actual completion" percentages in the Text field I mentioned above
- Copy this column over to the % Complete field, which will automatically calculate completion percentages at the summary task level
- Copy this column back over to the Text field
- Re-set the Status Date so that the % Complete field is moved back to its original "planned completion" state, and the "actual completion" percentages are still stored in the Text field

It's not ideal, but it'll work.

I do have another question on a bit of a different topic, but I figure I will create a new thread since that may help other people who are searching for similar solutions on search engines.

Thanks again!