Thanks for the suggestions. Results:
--F2 puts a dotted square around the entry, but there’s no visible way to modify it. I can’t paste anything into it, and any text I type just appears into the search box above.
--I looked at the Add-on but I’m not a programmer, and the need to run multiple lines of code to change each of many tracks individually rules this out.
--But entering dates as YYYY-MM-DD in a custom text field makes them sortable chronologically. Not ideal, and not combinable in a search with the Date Added entries that are OK, but better than nothing for the specific genre for which I want to use this.

Try F2 in the Filelisting and see if that works (I'm unsure).

If that doesn't a work you may want to check out this Addon: https://www.mediamonkey.com/addons/brow ... ql-editor/

Costum fields are just text fields, neither numeric nor date fields.

And if the answer is “you can’t without a database editor” (bummer), how about if I use one of the custom fields instead? What’s their data format? I.e., in what format should dates be entered in a custom field to be able to sort chronologically?

Somewhere in the long history of migrating my MMW library across a progression of versions, PCs and drives, the Date Added for many tracks got overwritten by a later date. I want to correct them manually (if only approximately) from other records, but MMW 2024 won’t let me type in that field (under Properties/Details). How can I correct them? This is an important sort field for me.