Verified working on Thunderbird Daily 104.0a1 - 20220722094822 (linux64).
Tested starting Thunderbird with -calendar argument when no other instance is running; verified that the Calendar tab is loaded and in focus on startup.
Tested running "thunderbird -calendar" when an instance is already running (with no calendar tab). Verified that the running instance opens a calendar tab and switches focus to it.
Tested running "thunderbird -calendar" when an instance is already running with a calendar tab open, but the mail tab active. Verified that the focus switches to the existing calendar tab.
Verified working on Thunderbird Daily 104.0a1 - 20220722094822 (linux64).
Tested starting Thunderbird with -calendar argument when no other instance is running; verified that the Calendar tab is loaded and in focus on startup.
Tested running "thunderbird -calendar" when an instance is already running (with no calendar tab). Verified that the running instance opens a calendar tab and switches focus to it.
Tested running "thunderbird -calendar" when an instance is already running with a calendar tab open, but the mail tab active. Verified that the focus switches to the existing calendar tab.