With preferences you make concerning single files and folders it's easy to lose track of which files you have currently set as whatever you needed them to be. This is especially important for shared files and folders since you don't always want them to be shared with everyone.
Good thing there is a list with all shared files hidden on your system - to get to it search for Computer Management in the Start menu.
On the left pane of the CM window, browse for Computer Management (Local) > System Tools > Shared Folders > Shared:
You'll get a list of items here that are shared by your computer with path and description given.
There's one important feature missing in Thunderbird that you will need when working with many different accounts, that is, reordering them. You won't find any option for this in the settings, nor is there any obvious way. The only one I found involved editing the prefs.js file (close Thunderbird while doing so!), that is located in C:\Users\user-name\AppData\Roaming\Thunderbird\Profiles\[profile-name]:
Some people suggest changing the order of the user_pref("mail.accountmanager.accounts") parameter but this did nothing for me. What worked instead was setting the user_pref("mail.accountmanager.defaultaccount", "accountx") parameter.
Setting it will put one account at the top of the list - by repeating this process, you can order your accounts the way you want it! Just replace the number of the account (marked with x in the text above) with the one you want top.