How do I mark an recently copied email to the local folders as read?

Question

I have a message filter for a local imap account setup to copy messages to the Local Folders. I do this because the imap account is actually an exchange account with a ton of email and I can't keep all of my email in the main exchange account so I use an exchange online archive which is hidden to thunderbird due to compatibility. Copying to local folders allows archiving and full searching all while keeping keeps thunderbird very fast. Alternatively if I have more than lets say 50,000 emails synced over imap from exchange compatibility things become horrendously slow.
Currently I have a message filter that copies messages from my imap to Local Folders. If I try to mark it read after the move, as in while in Local Folders it does it afterwards and I then miss the message. My goal is to only mark it read in Local Folders.
The problem is if I try to mark the copied message as read it must do it prior to the copy, which ruins my ability to keep track of what I have and have not read yet.
I tried to put another filter under Local Folders that just marks all messages that come into local folders marked as read but it doesn't take unless I run it manually on the folder. My understanding is that this occurs because the copy doesn't happen at the same time messages are synced.
How can I have it so the messages in the local folder are marked as read?

Answer 1

Done some searching and located an addon which is not auto run, but is quicker than writing filters etc. It creates a button/icon to use to mark all emails in selected folder as read.
* https://addons.mozilla.org/en-US/thunderbird/addon/mark-all-read-button/
'''How to install addon:'''
Download to desktop.
In thunderbird
Tools > Addons
Click on gear wheel icon and select; Install addon from file'
locate the file you downloaded and click on Open
You may need to restart Thunderbird at prompt.
'''Second option:'''
If you do not want another icon to add to toolbar - it does get messy if you keep adding icons :) then there is another method of adding it to the right click drop down context list of folders.
Make hidden files and folders visible;
* http://kb.mozillazine.org/Show_hidden_files_and_folders
In thunderbird
* Help >Troubleshooting Information
* click on 'Show folder' button
* '''Close Thunderbird now - this is important.'''
It will open showing Profile folder name contents.
You will see a 'Mail' and an 'ImapMail' folder plus other stuff.
* Create a new folder called '''chrome''' Note the spelling. It should be in same location as 'Mail' folder.
* Open Notepad
* Copy paste all the section between the two lines below
* save the file as '''userChrome.css''' in the '''chrome '''folder - note all spellings.
then restart thunderbird.
Right click on eg: Local Folder Inbox
you should see an option 'Mark folder read'
<pre>
* Do not remove the @namespace line -- it's required for correct functioning
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
#folderPaneContext-markMailFolderAllRead {
list-style-image: none !important;
</pre>
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