Anṣuf ar Thunderbird n izegrar.
Rnu timahilin neɣ iɣunab nniḍen akken ad terreḍ Thunderbird d ayla-k.
MdelAcegger n Mark All Read Button sɣuṛ wilf21
Yettwasezmel 5 ɣef 5 n yetran
Dear @DS, your suggested edit works perfectly on v68. Thank you so much.
Oh, except that it seems to disappear from the TB toolbar each time I restart TB :(
Further investigation shows it only does not persist on the Menu Bar (which is where I always have located it). It remains ok on the Mail toolbar, though.
TB68.2.0 64 bit
Ma ulac aɣilif ini-d acuɣeṛ:
Akken ad ternuḍ tigrummiwin inek, yessefk ad yili ɣur-k umiḍan n izegrar Mozilla.