Right now, there's no way to move tabs between windows on mobile.
Safari's current implementation offers a context menu on long press for this:
Even better, Orion's sidebar tab view could offer the common multi-select pattern in iOS of "Edit → multi-select → menu item". I.e., a two-finger tap or two-finger swipe would select tabs in the sidebar, then allowing users to select options from option bars that appear on the screen.
Here's what that looks like with a selection of tasks in the current OmniFocus 4 beta: