I would recommend opening a separate topic for that as it’s not relevant for the current beta. Then you can also ask the developers of those add-ons to chime in. They probably know best how feasible an integration would be.
Regarding the multi-window add-on, while certainly useful in some cases it doesn’t seem to be of use for the majority of users, but would merely be a complication for them. As can be seen from the reviews, there are also certain issues with it that are probably inherent to the functionality rather than caused by the implementation. That’s perfectly fine for an add-on where users deliberately choose to use it, but anything integrated directly in Anki has to adhere to higher standards of reliability and robustness.
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