From the main menu bar:
Events and Tasks (Alt-N) - Calendar

christ1, I'm assuming you you mean the the main menu bar in the calendar, but, in any event, I can't get Alt N to do anything in calendar or thunderbird. Perhaps I have a different version of Lightning. Mine is 2.6.5.

There is only one main menu bar in Thunderbird.

When you press Alt or F10, this brings up the main menu bar. Do you see an 'Events and Tasks' item there?

Can you post your Troubleshooting Information?
Help (Alt-H) - Troubleshooting Information

I feel like we're using different programs or at least different versions. When I press Alt or F10 anywhere or everywhere in Thunderbird nothing happens.

My version does have a shortcut to the calendar, which is Control 8. I can use that easily enough, but I was used to having a Calendar tab to click on and had hoped to get that back. Even if your suggestion worked, it wouldn't be what I was looking for, so I guess I'll resolve myself to using the keyboard shortcut I have.

Thank you for taking the time to try and help me.

Art Timm Anchorage, Alaska

I feel like we're using different programs ..."

My best guess is you did do some sort of customization to your Thunderbird you didn't mention in any way.

The Troubleshooting Information would help to determine that, so it's up to you how you want to proceed.

I may have changed some setting. I don't know. As I said though, in any event I'm going to live with the key-stroke shortcut I have and, accordingly I've marked my question as answered.

Once again, thank you for the time you spent.

Art Timm