For problems with add-ons you should contact the extension author.

I thought it was important to post here as Mozilla showed the Toolbar Buttons as compatible with TB 60.3.0, and it isn't on my TB.

Manotee said

I thought it was important to post here as Mozilla showed the Toolbar Buttons as compatible with TB 60.3.0, and it isn't on my TB.

Compatibility s not an alternative name for functional, or without bugs. When add-ons are reviewed for inclusion in ATN, they are not extensively tested for bugs. The reviewer will probably be using Windows. but they might just be using OSX or Linux. There are checks to see the add-onis not spyware and that your privacy and security should not be compromised. But setting the version compatibility level is largely left to the add-on author.

If the author finds a bug, they will be able to get an updated version of their add-on out to their users much faster than we can realistically do something to block the add-on. Blocking the add-on is generally seen as a last resort and usually applied to add-ons from major corporations like anti virus vendors that actually break Thunderbird for general use as a mail client.

The add-on doesn't work in TB 60, and the author is aware of this:

https://codefisher.org/forum/thread/35116/

but I suggest you try the Custom Button Maker, i.e. download an xpi file and install it in TB. I tried this recently and it worked.