VDI pools are tenant scoped (not ‘Public’). These would have to be created within the tenant you desire, and than you will see within the sub-tenant role.
No, this does not store more than 1 key. However, if you are using this more globally for console sessions to broker (VDI Gateway), you can set a gateway on a cloud or within the appliance settings (global) to utilize only 1 worker instead of having to assign per pool.