As usual with IBM MQ, you have be careful with terminology. My understanding of MQ "clustering" is that it's more about load balancing than high-availability failover. In a load balancing scenario it defeats the purpose if you're connecting to multiple points in the cluster from a single application instance.
I think what you're talking about is called "multi-instance queue manager", and that *is* designed for high-availability failover. Unfortunately, with IBM MQ's Java client a multi-instance queue manager connection is only supported in JMS Mode. You cannot use it with IBM MQ Native mode. Because of reasons, I guess.
If JMS mode works for your purposes, then create a new 'Direct JMS Connection Factory for IBM MQ' asset. Make sure 'PRO' is enabled, click the '+', and and find the 'Connection Name List' parameter:
Note that it's currently under the 'Advanced' category, but I think it belongs under 'Connection' and I'll be fixing that soon.
The format of the 'Connection Name List' parameter is 'host(port),host(port),...'. You will also probably need to *remove* the standard 'Hostname' and 'Port' fields with their respective trash icons:
Note that there is currently a bug where the 'Hostname' and 'Port' parameters will be added back in the next time you open the asset editor; I'll be fixing that as well.
There are also two other parameters to be aware of: 'Connection' -> 'Client Reconnect Options', and 'Connection' -> 'Client Reconnect Timeout'. Their tooltips already give you all the information I know about them.