Try this, as I think it should work: - follow the tools>import>import from a file menus until you get to the vcf choice. - click to open a vcf file. at this point, press cntl key while highlighting multiple vcf files and click enter key. the files should load. If you have a large quantity, you might start with 5 or 10. Good luck.

David, thanks for the suggestion. I tried that several times, and I was only able to get one highlighted and entered as previously. Thus a long and tedious task.

Here's a fairly easy workaround *IF* you're comfortable with the command line, and if your VCF files are all in one folder. This uses a DOS command, but there are equivalents for UNIX/Linux and, I presume, Macs.

Open up a CMD/terminal session in the containing folder. At the command line type:

copy *.vcf AllAddresses.txt

"AllAddresses" is an arbitrary name, it can be whatever you want, but the file MUST NOT have a .VCF extension. When you run that command it will concatenate all the VCF files onto one big file. When it's done, and it should just take a second, then rename that file from .TXT to .VCF. This file is now suitable for importing into your Thunderbird address book.

[later edit]... See my post below - the correctly command should be:

copy /b *.vcf AllAddresses.txt

Thank you, Lin. I noticed a similar solution posted a few years back, but I was uncomfortable with the approach. You clarified it. Thanks. :)

I just realized that I made one important mistake! I was thinking that all VCF files were straight ASCII text, but apparently not, apparently they can have some non-ASCII characters in them. Therefore, to make a valid "Big VCF" file you need to use the command line:

copy /b *.vcf AllAddresses.txt

The "/b" switch tells the copy command to treat the files as binary. If you don't do that, Thunderbird may give you an error message, and while it may still import the file, there might be some corruption in there (although I couldn't find any.)

Oops!

There are also online VCF merger sites, and probably programs you can install locally to do it if the command line isn't your thing. I found this one and it works and *seems* safe and easy, but I can't vouch for it. It claims that your files are not actually uploaded, that all processing is done locally, which is good.

https://vcf-file-merger.com/

See https://support.mozilla.org/en-US/questions/1280605