If you want to select multiple resources, you need to create a checkbox input (not a radio input) and configure it if you are in splunk web (this configuration is developed in splunk-Viz manual), otherwise if you want to modify directly in your source code, write the scripted input like follow instead your input type radio :
<input type="checkbox" token="Sourcetype" searchWhenChanged="true">
<choice value="*">All</choice>
<populatingSearch fieldForLabel="Host" fieldForValue="Host">index=idx_cat |stats count by Sourcetype</populatingSearch>
<prefix>(</prefix>
<suffix>)</suffix>
<valuePrefix>Sourcetype="</valuePrefix>
<valueSuffix>"</valueSuffix>
<delimiter>OR</delimiter>
</input>
Thus, with this, you are going to select multiple resources.
Splunk 5.0.5
What version of Splunk are you using?