Rated 4 out of 5 stars

Thanks for reviving this plugin.
And also thanks to Christian Eyrich for creating it of course!!!
TB should already have had this build-in.

I was searching for something like this for a long long time.
Dunno why it never popped up in searches (though, I never thought of using the keyword 'toggle').

Anyways,

The code in this version (0.5.1) has not really changed compared to the original version made by Christian Eyrich, except for three lines where a 'for in' statement is replaced with a 'for of' statement. Other than that, and the house-holding stuff of course, everything else is just a copy-paste.

'for of' is better and a bit safer, but other than that has no effect at all on upwards compatibilty I think? Makes me wonder if the original version is actually incompatible, or if it would be just a matter of updating the compatibility flags to include later clients.

...


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PS:

Locale = nl
Description = Voegt de mogelijkheid toe om berichtmarkeringen 'Beantwoord', 'Doorgestuurd' en 'Geheradresseerd' te wijzigen.
Label Replied = Als beantwoord
Label Forwarded = Als doorgestuurd
Label Redirected = Als geheradresseerd

This review is for a previous version of the add-on (0.5.1). 

The older versions of Thunderbird don't support the new construct. The newer versions of Thunderbird don't support the old construct. That's the whole reason why I had to fork this add-on and create the new version. The compatibility ranges on this incarnation of the add-on are correct and necessary.
Thunderbird 20 was released four and a half years ago. I don't think it's unreasonable to expect users to be running a version of Thunderbird less than four and a half years old, especially since the older versions are unsupported and have unpatched security holes in them.
P.S. Thanks for the translation, I've just released version 0.5.2 with it added.

Rated 4 out of 5 stars

My only criticism is that, after installation, the previous version is neither removed nor disabled. That should either be done automatically or new users should be advised to do so manually.

This review is for a previous version of the add-on (0.5.1).