What I did in the past was review the messages in the Inbox. I’d delete those emails that I didn’t want to save, which left the emails that I might want to refer back to in the Inbox(es) folder.
Yes you can still do exactly the same in V10.
You can click on either your account inbox directly and review and delete any emails you don’t want. Any emails not deleted will still show in All Inboxes and still show in the account inbox.
Also any emails “not read” will still show in the Favourites Unread folder at the top left, as well as still show in All Inboxes and in the account inbox.
If I delete it in unread, will that delete it from the account’s inbox?
Yes if you delete an email in the Favourites Unread global folder, that deletes it from the account the same as in the previous eM Client versions. The unread folder is designed to show you the all the unread emails from all your various accounts and “is not a separate copy of that email”.
So If you then deleted an email in the unread folder that was from an account Inbox and you then wanted it back, you would need to then go to that account trash folder and drag / move it back to the account.inbox.
Also like in the previous eM Client version, once you have read an email in the Favourites Unread folder, it will then “only show in the account”.
It would be easier for me if I could control which categories appear in Inboxes and which in Unread.
As I advised further up in this thread, you can control what Inbox Categories you have via either “right clicking on any Category and enabling or disabling Categories in the drop-down menu” as per @Quesito example in the following thread, Or you can alternatively “drag the message to the Category you want for future” messages.
You can also go to “Menu / Settings (Preferences) / Mail / Categories” where you can also select the Categories you want, Or “Disable all Categories” if you don’t want any Categories and want all your emails in the one Inbox like in V9, by clearing the Show Categories box at the top and then saving the Settings.
The only option you have “to not show emails in the Favourites Unread global folder” in V10, is via “Menu / Settings (Preferences) / Mail / Read” where there is options at the top to eg: automatically Mark messages as read after moving to Trash, & Mark messages read after move to Junk, & Mark messages read after move to Archive.
So if you eg: setup rules in eM Client to automatically move specific Account inbox emails “when they arrive in your Inbox” to either the Trash, Junk or Archive folders, then they won’t show in the Unread folder as will be already read.
Apart from those options with a Rule, “there is no control over what emails show in the Unread folder”. As I mentioned previously it’s designed normally to show you all account unread emails.