Note:
This addons options dialog has now to be opened in Thunderbird 78 from the Addons Manager Tab using the wrench icon button (from up 78.10) or the little menu at the 3-dot-icon button (before 78.10):

https://support.mozilla.org/en-US/kb/thunderbird-add-ons-frequently-asked-questions#w_how-do-i-configure-add-ons

Note:
This addons options dialog has now to be opened in Thunderbird 78 from the Addons Manager Tab using the wrench icon button (from up 78.10) or the little menu at the 3-dot-icon button (before 78.10):

https://support.mozilla.org/en-US/kb/thunderbird-add-ons-frequently-asked-questions#w_how-do-i-configure-add-ons

Internal change / update for the WindowListener-API.

Note:
This addons options dialog has now to be opened in Thunderbird 78 from the Addons Manager Tab using the little menu at the 3-dot-icon button.

https://support.mozilla.org/en-US/kb/thunderbird-add-ons-frequently-asked-questions#w_how-do-i-configure-add-ons

The add-on has been completely revised again in version 3.x to be available as a pure MailExtension for the upcoming Thunderbird 91.

Note:
The options of the add-on can now be found directly in the add-on manager under the open list entry of the add-on (no longer in the tools menu).

New features:

• The display of the quotation levels can now optionally also be activated for the compose window.
• A separate set of colors is used for light and dark mode themes
• Added / incorporated "Quote Collapse" feature, which has to be enabled in the options dialogue. Per default citations were not collapsed.

Features currently no longer possible:
The display of the quote levels in printed messages can no longer be adjusted using the add-on. Maybe this will be possible again in the future.

The add-on has been completely revised again in version 3.x to be available as a pure MailExtension for the upcoming Thunderbird 91.

Note:
The options of the add-on can now be found directly in the add-on manager under the open list entry of the add-on (no longer in the tools menu).

New features:

• The display of the quotation levels can now optionally also be activated for the compose window.
• A separate set of colors is used for light and dark mode themes
• Added / incorporated "Quote Collapse" feature, which has to be enabled in the options dialogue. Per default citations were not collapsed.

Features currently no longer possible:
The display of the quote levels in printed messages can no longer be adjusted using the add-on. Maybe this will be possible again in the future.

Added CSS and Options to handle Darkmode Themes.

The add-on has been completely revised again in version 3.x to be available as a pure MailExtension for the upcoming Thunderbird 91.

Note:
The options of the add-on can now be found directly in the add-on manager under the open list entry of the add-on (no longer in the tools menu).

New features:
The display of the quotation levels can now optionally also be activated for the compose window.

Features currently no longer possible:
The display of the quote levels in printed messages can no longer be adjusted using the add-on. Maybe this will be possible again in the future.

Fix issue in options dialog (dark text on dark background) with some lightweight themes (may be the related issue is a Thunderbird bug)

Version 1.0.5 changes the homepage URL to the correct new one on ATN