Provide a UI that allows storing a list of emails that can be read later. I am
usually using single message tabs for this, but this can get messy quickly (too
many tabs) and sometimes Tb resets the session so it is not 100% reliable. A
dropdown list similar to the one on the quickMove button would probably be a
good enough start for this feature. Of course it must restore the list on Tb
startup (and not be reset like quickMove).

Created an attachment (id=8049) [details]
Prototype Menu

Suggestion for a UI:

1. Reading List (Bookmark) button, which accepts drag and drop
2. Counter of messages currently contained
3. dropdown menu
3a) reset list - removes all entries
3b) Add current mail - should add the email curently viewed, but coiuld
potentially also be used to bookmark other items? (Folders / Appointments / Web
Sites when on a content tab? - this poses a question whether the location on
the QF toolbar is ideal, as it is not always visible) 
3c) List of Mails
    Clicking a mail opens it in a single tab (advanced behaviors such as
opening a new window are subject to configuration
    Right-clicking a mail offers to remove email from the list

Nice to have:
  It would be great if the bookmarks persist correctly even if the mail was
moved to a different folder in the meantime.

Created an attachment (id=8050) [details]
4.1 prerelease 77

Prototype with the feature.

To make it visible use the "Reading List" checkbox on the QuickFolders Pro tab
in QF options.


For configuration of the mail label the folder can be toggled using:
extensions.quickfolders.bookmarks.folderLabel - currently this only affects
newly added items, as the label is saved in the file completely.

Right click above checkbox for (more) options, as usual... 

Storage:
bookmarks are not stored in about:config anymore but use their own file
"quickFoldersBookmarks.json" in the profile's extension folder. 

This is better for performance. Eventually I am planning to move the
QuickFolder tabs storage into a json file as well, as the config database
complains about the amount of data impacting performance when many folders are
stored.

Created an attachment (id=8056) [details]
4.1 prerelease 137

Improved the file persistence and tested in Postbox also. I made some more
decisions on the label coloring, it is now gray for the reading list and red
for the "quickMove" icon. 

This way both tie in more with the color scheme of the operation (red should be
an exeption color and not displayed permanently, so this would be
counterproductive for a persistent reading list. Also we do use a red
background for the searchbox in quickMove; so it makes moire sense to have red
coloring for the number of mails to be moved)

"Add current item" works now for single messages and a single message tab. I
plan to support content tabs (web pages) in a later incarnation of the feature
(but not yet in release 4.1) - just waiting for feedback from my users first.