Welcome to Firefox for Android Add-ons.
Add extra features and styles to make Firefox for Android your own.
CloseReview for Window Master by NoSpeak
Rated 4 out of 5 stars
Right now merging and moving is tricky, as you can only create a new window from the initial window tabs. Created window tabs only have merge option.
It would be nicer if it just allowed you to split number the windows and then allow you to move tabs to a numbered window. So 0-3 and you select which window the tab should be moved to.
All tabs have both move and merge options, so your first remark makes no sense to me. (You do need to have multiple regions per screen to be able to distinguish between screen regions and existing windows as a target).
Numbering windows or screens is possible, but the order is arbitrary and therefore numbers are not very helpful (except for minimized or covered windows).
To create your own collections, you must have a Mozilla Add-ons account.