I presume you are referring to the accounts llisted on disk. click to account settings, click the server settings pane for an account and the bottom row of right side of scxreen will show local directory.

No, I want to save a complete account on CD. The solution you proposed maybe works on Windows, but I have MacOS. I cannot find the the place in Server Settings, where the account is saved on my disk. Sorry

1. To see provider information for each account, David's suggestion: Access account settings. There are several ways to do this. One is to right click on an account name in the folder pane and click on "Settings" in the drop-down menu. Another is to click on the three-line button on the far right of the top toolbar and click on "Account settings" in the drop-down menu. Either way, on the tab that appears next, click on "Server Settings" below an account name in the left pane. In the right pane, note the server name. It should give you a good idea who the provider is. The user name below the server name identifies the provider account. Repeat for each account.

2. There are various ways to "save a complete account on disk". You could copy or export your whole Thunderbird profile with all your account settings and messages; copy all the account's messages in the format used in Thunderbird; export all the account's messages for archival use or use in another e-mail client; copy or export only messages that are on the server or those messages plus messages that were retrieved from that account but are now stored locally, et cet. What you do depends on what you want to do with the data that you put on CD. What do you want to do with it?

You may want to rename the accounts to something more descriptive so you know which is which.