I am unsure whether that feature is available without an add-on? I am using "Nostalgy++" https://addons.thunderbird.net/en-GB/thunderbird/addon/nostalgy_ng/?src=search intensively for this. I.g. their "go" (to folder) command allows you to start typing parts of the folder name that you remember and it will show you the list of folders with the search string in the name, even if these are sub folders of other folders. I cannot work quickly without that add-on, one of my most important ones. Hope that helps.

Michael, thank you. This is an interesting add-on and does solve the problem of finding a folder. I have figured out how to do that, but it looks like it offers much more. I have been able to decipher how to conveniently conduct searches in general. If you have any quick tips I would appreciate it.

I haven't marked problem solved since I am unsure whether that closes out this dialog.

I constantly use it for - selecting the emails that I want to deal with (my command is the "~") - "g" (go to a folder), - move the selected emails to a specific folder (I have define "r" for the move command rather than the default "s" which conflicts with the default "s" to star emails)

The add-on offers more like creating email filters but I do not use that in Thunderbird. I define my filters and rules at the server end rather than in the email client (which needs to run to process filters).