If you look at properties of a folder called normal in Thunderbird, it points to a Windows folder named "normal", not "normal.sbd. So I suspect you shouldn't be pointing to .sbd folders.

Or if you think there is a bug in the localfolders addon, see https://github.com/cleidigh/Localfolder-TB/issues

The standard configuration of Thunderbird will show many local folders if they are stored in the right place in your profile. I believe that you should also be able to store many folders outside your profile in the right directory structure and have them all appear in Thunderbird if you prefer to keep all your local folders somewhere else.

So you should not need an add-on for what you want to do. Adding more folders under Local Folders is indeed the right approach.

Unless I misunderstood and you actually want different local folders stored in different locations. Do you?

Let me explain the problem by simple example.

Suppose I want to have a local folder C:\TBOFFLINE where I store TB email. Additionally, I already have two archived TB folders called DATA1.sbd and DATA2.sbd that I want to have available within the local folder C:\TBOFFLINE so that both are accessible from the Local Folders menu in TB. These are not new folders directly created *within* TB, they already exist as separate files.

Option 1: First link the new and empty local directory C:\TBOFFLINE in TB, and restart. TB automatically places Trash.msf and Unsent Messages.msf files in C:\TBOFFLINE. If I now copy DATA1.sbd and DATA2.sbd folders to C:\TBOFFLINE, and restart TB, neither DATA1 nor DATA2 folders show up in Local Folders. However, if I change the local directory to C\TBOFFLINE\DATA1.sbd (pointing directly at one of the TB offline folders) and restart, then the DATA1 folder+subfolders+ emails are present in Local Folders. Same for DATA2 on its own, they are both valid containers of TB folders and emails. But how to get both?

Option 2. Before linking the local directory C:\TBOFFLINE in TB, copy both DATA1.sbd and DATA2.sbd to C:\TBOFFLINE. Restart. Now a new folder, DATA1.sbd.sbd plus DATA1.sbd.msf is created within C:\TBOFFLINE, the Local Folders directory in TB shows a folder DATA1.sbd and it has associated sub-folders that are accurately named, but the sub-folders themselves are empty. This option ignores the second data file, and failed to display contents. Complete failure here.

Option 1 was therefore partially successful, but I’ve yet to find a way to have the system map the contents of more than one externally-supplied .SBD folder. With Outlook, one simply points to external files (PST) with their individual local drive locations (not necessarily one folder) that are immediately available in the application.

I believe your example should work, and don't understand why it doesn't. Maybe the format isn't exactly correct.

Is importexporttoolsng add-on installed into Thunderbird capable of importing the messages if you point them to those directories?

I have reproduced much of this problem on my computer, or at least a similar problem. See attached before and after screenshots.

I started with sub-folders that did not have an sbd extension. That was an oversight. I meant to reproduce Richard's situation with the sbd folders. Thunderbird created sub-folders with the sbd extension, but did not move the mbox files into them. Inside Thunderbird were empty folders. When I moved the mbox files myself into the sub-folders that Thunderbird had created in the file system, folders in Thunderbird remained empty.

Richard, since Thunderbird is not dealing properly with the file system, the only way I see to accomplish your objective is to put all your mbox files, maybe one sub-folder at a time, in a flat structure (without sub-folders) into C:\TBOFFLINE, then put them into sub-folders within Thunderbird. Thunderbird will then create the structure in the file system that it needs.

How many mbox files do you have in your two sub-folders? I'm guessing that it is more than a few, in which case this process may be onerous, but maybe not very onerous because you should be able to select and move many files at once.

Please file a bug report for anything that is not working correctly. Thanks.

Thanks to all for your help.

I filed a bug report.