I would try ddrescue first with the other one, but since I'm going offline soon for the day I'll leave here the instruction for the other option in case you want to try that instead.
I'm going to assume the rescued disk is disk1, if it's not adjust as necessary, also you need a new disk for disk3, if you want to rebuild it, if you just want to see if it can be emulated you can use the old disk for now:
-Tools -> New Config -> Retain current configuration: All -> Apply
-Check all assignments and assign any missing disk(s) if needed, including the cloned disk1 and the new (or old) disk3, if it's a new disk it should be same size or larger than the old one
-IMPORTANT - Check both "parity is already valid" and "maintenance mode" and start the array (note that the GUI will still show that data on parity disk(s) will be overwritten, this is normal as it doesn't account for the checkbox, but it won't be as long as it's checked)
-Stop array
-Unassign disk3
-Start array (in normal mode now), ideally the emulated disk3 will now mount and contents look correct, if it doesn't post new diags
-If the emulated disk mounts and contents look correct and you are using the old disk stop here, for now you can access its contents using the emulated disk, if there's a new disk3 and you want to rebuild it, stop the array
-Re-assign disk3 and start array to begin.