The easiest way (and if you're familiar with PHP) is to create custom blocks yourself.
If in the plugin settings there is no way to choose which groups will appear in the list, then this is a problem with the plugin .. You can then use the standard IPB blocks. The Members block (System> Members), choose the groups that will appear, choose the Currently Online option and the Sort by Last Activity option.
He will make a staff online, but will show with the delay of 5 minutes and will disappear when no one is online, as it should be.