Determining unused config

You actually can determine this, and you don't need BigIQ to do it. If you look at the statistics for your virtual servers they will report all traffic since the last reboot. You can also manually reset the statistics. Then you just need to look for numbers that are zero or close to it.

Once you have identified the obsolete virtual servers, you can disable them and see who yells. As long as you have the configuration documented, you can then delete the virtual server after a suitable time period.

You can also upload your qkview to ihealth and it will tell you if you have objects that are not referenced.