Theoretically it'spossible to achieve this, although it's not quite trivial. What you can try is to mimic the settings from the current By Tag filtering, and create new definitions that resemble them so you can filter by your custom taxonomy. Please go to Administration->Settings->Advanced->Libraries->Controls->ImagesBackend->Views->ImagesBackendList->Sections->Sidebar and inspect how the definitions are constructed for the ByTag section. Basically you'll need to create a new section and add a DynamicCommandWidgetElement and a CommandWidgetElement with similar settings to the one that ByTag section is using if you want to achieve similar functionality. Please let us know if you need any additional information on this.
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