Right-click any of the column headings, e.g. Date, and a list appears showing all the possible columns. Select "Recipient:" and de-select "From:".

Thank you! ! That solved HUGE problem quickly and simply.

Here's another question: the "search" function in my old Thunderbird program allowed me to search by "subject" or "sender." This newer Thunderbird does not seem to offer the "subject" option. Unless I'm missing something. Thoughts?

The most prominent search tool in Thunderbird is the global search, which indeed doesn't offer specific searches, though once it has located your string, does offer some refinement options.

The QuickFilter can do what you ask, though it doesn't become obvious until you type in a search string.

View|Toolbars|Quick Filter Bar - or there will be a toolbar button to enable it, if you can't already see it.

Or you may be thinking of the original search, still available via ctrl+shift+f.

Thanks! You're a whiz!