There’s no way to automate this as far as I know, but you can take a single-line text column and convert its contents into a linked record field (watch the video under “Linking Existing Tables of Related Records” in this support article). So maybe you could intermittently convert the linked record column into a single-line text field, copy and paste the text values you’d like to convert over that column, and then reconvert the column into a linked record column? I don’t think this would be the convenient solution that you’re looking for, unfortunately. I’ll pass on your feedback to the team.
I was really looking forward to using Airtable to manage a whole host of my volunteer organization’s data, but the very first thing I tried to do is blocked by this missing feature… My case is simple: I have a growing list of sign-ins to meetings, and I want to keep a derived Membership table that identifies all unique members who have gone to meetings. I can easily make this table at any given time and do aggregations (like a count of meetings attended), but am I to believe there is no way for new additions to the sign-in sheet to be aggregated into the derived Membership table? I would have thought this was pretty basic.