There used to be an add-on that allowed the export of filters but it doesn't seem to work with recent versions of Thunderbird. The clearest advice I could find for you on line is here: http://ask.systutorials.com/671/how-to-export-and-import-message-filters-of-thunderbird You will see that it's not at all a straightforward process, not least because the filters are tied to particular accounts.

There is no need to export or import anything.

The file that stores your filter settings is called "msgFilterRules.dat". Each account will have its own "msgFilterRules.dat" file, stored in the "Local Directory" for the account in your profile. The Local Directory is specified at the bottom of Tools -> Account Settings -> Server Settings, right by the Browse button. The filters for Local Folders are stored in the Mail\Local Folders directory in the profile.

If you want to duplicate an accounts filters in another account you don't need to create them again. Exit Thunderbird and copy the "msgFilterRules.dat" file instead. If the account is in another profile and it uses custom headers you will also need to copy the mailnews.customHeaders setting from prefs.js.

There is no support for sorting rules in the message filter window. If you have problems finding a filter try using the Filter Of Filters add-on. However, if you have hundreds of rules it is usually easier to edit them by editing the "msgFilterRules.dat" file with a text editor (not a word processor).

@Justwondering25 Has your question been answered by the answers that were provided?