That would be via this addon https://addons.thunderbird.net/en-US/thunderbird/addon/bidi-mail-ui/?src=ss

unfortunately this add on also doesn't work with me and appear a message after trying to install it that this add on couldn't be installed because it has not been verified.

I'm using 102.3.1 I downloaded and installed with no problem so let's check the method you used.

I went to this: https://addons.thunderbird.net/en-US/thunderbird/addon/bidi-mail-ui/?src=ss I clicked on 'Download'

This file : bidi_mail_ui-0.13-tb.xpi was downloaded into my 'Downloads' folder on computer.

In Thunderbird Menu icon > Addon and Themes Select 'Extensions' in left pane click on the gear cog icon to see dropdown and selected 'Install addon from file' Went to the 'Downloads' folder and selected the 'bidi_mail_ui-0.13-tb.xpi' file and clicked on 'Open' I was asked to accept - clicked on 'Add' It installed and I clicked on 'OK' Addon now listed in Extensions. For BiDi Mail UI , I clicked on the spanner/wrench icon and I could make settings.

Thank you Toad-Hall that's help me a lot and it's working now. Really appreciated>