If you want to get an overview of which inputs are configured to go to which index, I guess you could get that using the btool command:
./splunk cmd btool inputs list
I'm not sure to understand your need: do you want to send all the inputs in one index?
To do this you have to insert in every room of your inputs.conf
If instead you don't want to insert this option in every room of inputs.conf, you can configure your Indexers to override index value.
To do this, you have to insert in every Indexers or heavy forwarder:
in your props.conf
[mysourcetype] TRANSFORMS-index = overrideindex
in your transforms.conf
[overrideindex] DEST_KEY =_MetaData:Index REGEX = . FORMAT = my_new_index
In this way, every event with sourcetype=mysourcetype will be sent to my_new_index.