There’s a tool for exporting “everything”. Of course you should use that need occasionally, or other techniques, to back up your Thunderbird assets generally… it includes your messages.

But what if you want to take a copy of just your contacts. Take a copy that you can use in any general app?

Easy!

Use Tools/ Addressbook.

From where that takes you, right-click on the name of the address book you want to export. (or click on the ellipsis after the book’s name.) You need that “export”… there are others, but they do different exports.)

You want to export to a “Comma Separated” format. That was the default when I went through the process while writing this for you.

A “Save As…” dialog will open. Use that in the usual way.

That will give you a .csv file, which you can load to spreadsheet (LibreOffice “import csv” help) or text editor or word processor. I’d recommend a spreadsheet. (For LibreOffice Calc, the delimiter is a comma, as is usual.)