@richardnairn welcome to the forum!
Please vote up (by liking the first post) this existing feature request --> https://forum.vivaldi.net/topic/92066/mail-panel-favorites-category-ability-to-reorder-and-hide-items-within-a-category which asks to add a "favorites" category and allow hiding unneeded elements within a view category.
While your request makes total sense, please allow me to invite you to trying out the very efficient workflow that Vivaldi mail is tailored to. Since Vivaldi is optimized for a multi account setup, so in that approach, a single INBOX folder (or any folder for that matter) is not all that relevant. Instead of focusing on folders, Vivaldi is optimized for filtering emails based on criteria and just hide all emails that do not meet the selected criteria.
How to get close to your preference to show INBOX:
Emails from all email accounts are displayed in the unified inbox views under "All Messages" regardless of which IMAP folder they are located. Specifically, "Unread" will show all unread emails in any IMAP folder. You can further narrow down what is shown here using the view filter toggles above the mail list. To show only emails from the INBOX folders of your accounts, unselect the "show custom folders".
General notes
All views have sensible defaults but will keep any modifications you make until you change them.
Vivaldi sports a very powerful search function, which makes almost any type of filing emails into folders unnecessary. (Check out the link in my signature about why email folders are evil).
All I ever do with emails from my many accounts is reading in Unread, replying/forwarding, and when I'm all done with an email, mark it as read, done.
All views other than Unread are only there to find older emails. I have hidden all those that I don't use (flags, custom folders,...) using the right click menu on the categories. You can also change the order if the view categories in the mail panels.
Hope this helps! Let us know how you get along.
