Bug module in SuiteCRM is used to track and manage product-related problems, commonly referred to as bugs, defects, or feature requests, either found internally or reported by customers. Default installation include Bug module, but hidden and hence not appear in module list. To appear in module list, remove from the hidden module setting. To do this, login as CRM admin page and go to 'Display Modules and Subpanels'.
In Display Modules and Subpanels, drag 'Bug' in the 'Hidden Modules' list and drop to 'Display Modules' list. Click save.