But fist there is issue with diagram and also in module/Accounts/varders.php there is only relationship between primary Accounts and children Cases as ONE TO MANY relationship.
Hi, when you have relationship one-to-many that means every CASE can have only one ACCOUNT and that if you look to CASE table field, you will find there accound_ID field from which you can get the account id and if you want get how many CASES use/are under ACCOUNT id it is created index idx_account_id which collect this information.
By study of relationship by migration from old SuiteCRM to fresh new one 7.14 i see that this table has any reason to be created and it’s bug.
This table should have only relevance if will between cases and accounts, where account will primary side the relationship many to many. But on fresh install there is no relationship.
Ok. I suppose that the migration avoids deleting tables.
But if you are almost sure it’s not needed, then try returning it to something else, and see if anything breaks. If after a while you conclude it’s really trash, the delete it.