Go to : Content/PortalTeleport/Blueprints/Portals/BP_SameLevelPortalTunnel
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Add
-Drag it to your target level and set the scale to all axis 2.
-Add another portal for connection with same settings
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Set
Portal Render Quality -> Portal render texture resolution.
Connected Portal -> Select target portal to go.
Texture Render Target -> Select different from the portal attached to the target tissue for processing.(if you stream on same time multiple portal you must choose different textures).