Version 60 is no longer supported. As the software is free and there are no costs associated with maintaining an up to date installation with the latest security patches only the current release version is actively supported. There is generally around a 6 week transition time when a new release comes out as not everyone can update immediately.

I note that you are using Windows 10 and Firefox 113, so it is not a limitation on your system that sees you using unsupported software that was release in 2018.

Now 1. I do not recall when the config editor was updated to the new format. I took the time to update the support article when the changes occurred, I think it was some time after version 60. But I honestly do not recall. It was years ago now. If your version does not follow the current documentation, perhaps you could update the version you use to a supported one.

2a. Setting a value to it's default will see it removed on the next start. That may not apply to typos. I have never had to try and remove one that I recall This advice would be as correct now as it was in 2013. https://support.mozilla.org/en-US/questions/958692

2b Only settings with a non default value are stored in the prefs.js file. Defaults are loaded in the code and don't need a settings file to refer to.

Perhaps you might want to look at why you are moving from a paid version of Thunderbird to a free one and going off to edit hidden preferences right away. Very few of the millions of users of Thunderbird will ever even edit a preference in the config editor. Let alone make an error in entering the preference name. Perhaps what you are doing is better approached another way.

I am rather interested in your choice of preference, accessibility.AOM.enabled is primarily a web page setting which is disabled in Thunderbird and Firefox by default. Why would you be wanting to enable it in Thunderbird? My understanding is screen reader technology works in Thunderbird with the setting disabled .

Version 60 is no longer supported. As the software is free and there are no costs associated with maintaining an up to date installation with the latest security patches only the current release version is actively supported. There is generally around a 6 week transition time when a new release comes out as not everyone can update immediately. 2a. Setting a value to it's default will see it removed on the next start. That may not apply to typos. I have never had to try and remove one that I recall This advice would be as correct now as it was in 2013. https://support.mozilla.org/en-US/questions/958692 2b Only settings with a non default value are stored in the prefs.js file. Defaults are loaded in the code and don't need a settings file to refer to. Perhaps you might want to look at why you are moving from a paid version of Thunderbird to a free one and going off to edit hidden preferences right away. Very few of the millions of users of Thunderbird will ever even edit a preference in the config editor. Let alone make an error in entering the preference name. Perhaps what you are doing is better approached another way.

Thanks for reply. Your answer to 2a and 2b were helpful although can't imagine why an option to delete any new added item would not be in order.

I've been editing with the config editor for yrs. both with Postbox (a similar app) and previous versions of TBird off and on as I kinda wanted to use TBird but it always lacked some of the capabilities of Postbox.

But currently my old version of Postbox is not scaling well enough in my new higher resolution Laptop. TBird is showing up better at my display settings in any Scale Layout choice. So was hoping to migrate to TBird.

Unfortunately with every upgrade of just about any software it's difficult to get the setting like you had them in the earlier versions (including the newer version of Postbox). So far still too many issues for me to commit downloading from the server with TBird, but will try a bit more with it.