The GOOD tab allows you to add bonus, strategic, and luxury resources.
In Civ3, if you have more than 32 resources, and resources that are both strategic or luxury resources are a multiple of 32 spaces apart in the resources list, the Phantom Resource Bug will appear. This will cause resources to appear in a city when they should not. For details, see the thread at https://forums.civfanatics.com/threads/keeping-resources-in-check-no-phantom-resources.391951/
The editor will detect when the Phantom Resource Bug would be triggered, upon saving your .biq file. It does not yet detect incorrect luxuryicons_small.pcx files as mentioned in the CFC thread.
You can resolve the Phantom Resources Bug (in version 1.33+) by dragging-and-dropping resources on the GOOD tab such that there are no strategic or luxury resources that are a multiple of 32 resources apart from each other.
The check for the Phantom Resource Bug can be disabled in Options --> Editor Settings.
As of version 1.33, the GOOD tab supports filtering the list of resources. For information on filtering in general, see this page; for information on the filters available for resources, see this page.