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I find myself now generally using a "master-stack" approach to window management with i3. More specifically, I have two "stacking" layouts (verticallyhorizontally) side-by-side, like so:
That is, I have a "master" stacking layout on the left and use a "stack" stacking (or splitv) layout on the right.
Now, i3 is a manual tiling manager which means that to move windows you can move window manually from the "stack" layout to the master - however it won't automatically move the current "master" to the "stack" layout when doing so (other dynamic tiling managers do usually do this in a master-stack layout).
We can however, simulate this basic concept with a bindsym which will move the focused "stack" window to the right (the "master" layout), focus up (to select the currently selected "master" window), move it right, and then focus on the (now new) master window. Add the following to your i3.conf file (I've found $mod+m works well for me):
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