About changing the column order in Opera's 'tree' views.
It is a rather hidden feature, that you can choose which columns to show in views like the mail messages list and the download manager. Right-click on any column header, and you can select the columns. You can also change the width of columns by dragging the divider between the columns. All this requires the mouse BTW. Note that, as opposed to the standard Windows list control, it is not possible to make the columns occupy more (or less) than 100% of the available horizontal width.
After adjusting the column widths with the mouse and closing Opera, the Preferences file (see 'Help > About Opera' for it's location) will contain a line that defines which columns are shown, with which width, and in which order.
The line in the Preferences file looks like this:
Mail View=0, 25600, 1, 1, 28091, 1, 2, 93822, 1, 3, 22216, 1, 4, 13770, 1, 5, 51200, 1, 6, 21298, 1
You see 7 triplets of numbers here. First is the column id, second the width and third the on/off bit. You can change the order of these triplets to move the columns around.
0: Status, 1: From, 2: Subject, 3: Sent, 4: Size, 5: Attachment, 6: Label
So by changing the line to, for example, this:
Mail View=0, 25600, 1, 5, 51200, 1, 1, 33773, 1, 2, 88400, 1, 3, 22146, 1, 4, 13656, 1, 6, 21223, 1
... the Attachment column will be shown after the Status column. Don't worry about the column sizes when editing, Opera will make it fit.