Need to understand which pages can have the flexibility of addition of a subtab

Hi team,

Could you please advice which pages in ERP can we add/remove/modify subtabs and in which page we cannot?

For eg, in the OM page on the left pane we have warehouse, payment etc subtabs which can't be modified, however subtabs on Service Request Summary and Asset Overview pages can be modified, so need to understand which is possible and which isn't?