RE: Now I have to take my hands off the keyboard and move to the mouse,

No you do not. You just need to learn the new methods.

I believe initial changes came in back in version 78.0 Loads of changes mentioned in more details here: https://support.mozilla.org/en-US/kb/addressing-email

The section you are looking for is : https://support.mozilla.org/en-US/kb/addressing-email#w_changing-recipient-type-how-to-move-recipients-to-another-address-field

using keyboard: Open Write which auto focus on TO field. If you immediately want to see a Cc field. Hold down 'Shift' key and use 'Tab' 3 times - click on 'Enter'

OR after entering email address move it to a Cc field via keyboard. enter email address in a To field then select it, use key on keyboard which displays right click options, press C twice to select 'Move to Cc' and press Enter.

Mouse: Right click on email address in TO field and click on option 'Move to Cc'

OR use the Contacts Sidebar Select address book. select contact, click on 'Add to Cc'

In version 91* there are further improvements: This is new and now opens the Cc: Ctrl + Shift + C More info: https://support.mozilla.org/en-US/kb/new-thunderbird-91#w_efficiency-where-you-need-it-most-improved-addressing-area-for-new-messages

It's still a classic case of trying to fix something that isn't broken. I shouldn't have to ask support how to do something that was obvious in a previous version.

Thank you for responding.

So where we used to simply hit tab (and had acquired substantial muscle memory to doing that), we now have the "faster and easier" options to use Ctrl + Shift + C or Ctrl + Shift + B or use the mouse.

Both of these "improvements" are more difficult to carry out for folks with arthritis and/or repetitive stress type hand/wrist problems.

It's still a classic case of trying to fix something that isn't broken. I shouldn't have to ask support how to do something that was obvious in a previous version.

It's an old cliche - 'Anything is obvious when you know what to do' and there is no shame in asking how to do something. That's the purpose of a Support Forum, to try and offer help.

Often, it is worth while using the Support Forum search function, you would have found that information in the Support Forum Help Articles or even in google search would get to those Articles. As a future reference, you usually find articles start with 'new' and 'thunderbird' and version number eg: 91 offer info on latest changes and they often have links to other helpful Articles.

Oh Good Grief! said

options to use Ctrl + Shift + C or Ctrl + Shift + B or use the mouse.

OR create the Cc line first - use Shift , tab 3 times to select Cc and press Enter Or type email and select/highlight, use right click key, then either use arrow keys or two presses of C and press Enter

OR use mouse or use Contacts Sidebar method.

Please note there has also been another improvement which you may have also noticed at the same link. If you use the Cc on a regular basis and therefore would prefer it to be automatically available when you click on 'Write', there is a setting on a per account basis. In the 'Account Settings' > 'Copies & Folders' for account, select the checkbox 'Cc these email addresses' If you do not enter any email address, it will auto display a Cc field with nothing entered when you click on 'Write'. This will save you considerable time opening it each time. If you add an email address, that email address will always be pre-entered in the Cc field.

EDITED: Thank you, I do use CC and BCC on a regular basis (multiple times per day). Changing that setting initially didn't seem to do anything at all (if left blank), but once I changed it for three of my email addresses, it did return things to a previous state (prior to a bunch of updates) when the CC and BCC were available as blanks on every email. Given my particular physical issues, etc., I think this is the most functional and easy set-up for me, even for email when I won't use a CC or BCC. [I think there is something wrong with the way my inbox is set up--a longstanding problem I've been living with, not something recent, and that is why I had to change it for multiple email addresses.]

I realize that we are supposed to read thru the lists of changes and new features every time we upgrade? But most of the time the upgrades happen at times when I do not have the leisure to do that. And when I do start out trying to read it, it is a bunch of things I don't understand quite honestly. I burn up my ability to concentrate and make sense of things while I am doing my paying work, and there is none left over.

Thanks again. This fix is a major improvement for me.

re : The easy thing for me would be to always have CC/BCC available and just tab thru when not needed....I do use CC and BCC on a regular basis (multiple times per day), but changing that setting doesn't seem to do anything at all if left blank.

Changing that setting in Account Settings > Copies & folders will not work on a previously opened Write window. So if you had a Write window already open, and then you changed that setting, you would not see anything in that window. It will also only work if the 'FROM' is the account which you selected the relevant checkbox. It also only works in version 91*

I have one account permanently set up to auto display a Cc field when I use that email address and click on Write. So I know it works perfectly ok in version 91.2.0 I've just also selected the Bcc for the purpose of producing an image. See below.

The trouble with the old setting was if you had several Cc or Bcc on many separate lines, you would be performing a repetitive change which is not good for people with RSI issues. People were asking for a way to do it once. The new way you only do it once and there are loads of different variations to do it.

Another way is to do it via the top 'Menu Bar' - use 'Alt'+'V' and then 'Alt'+'C'

Have you considered using the 'Contacts Sidebar' ?

For example: Click on Write and it opens with cursor focus in 'To' field. If Contacts Sidebar is not enabled then use 'F9' key If already enabled, 'Alt'+'K' gets focus on the 'Address Book', so you can select from choice. tab to search and use or tab to list and if you want a name begining with eg: H then clickon H to jump list select/highlight contact name and use 'Alt'+'D' to add selected contact to Cc field. If Cc is not already open then it auto opens.

Hi Toad-Hall. I just want you to know that you are VERY HELPFUL, and I really appreciate you. That did fix it. I just had to make the change for multiple email addresses, not just the one address that I use for the business-type emails that sometimes use those fields. Oddly, (with multiple physical/neurological issues) two extra tabs for every email seems less stressful for my left hand than those other key pressing options that you gave. Or at least that is my impression. Perhaps it is not true?

I think the long-standing overall setup and organization of my email was the problem. I have multiple address sharing an inbox and subfolders.

Anyhow. Thanks again. The time and patience you spent on me was really helpful. I'm learning a lot and will hopefully be able to solve more problems on my own (as I make the efforts).