Hi Deepak,
For using BRF+ custom agent for Asst Manager Stage, you should have some criterion to determine your Main Manager and the same criterion should be used in BRF+ to determine Asst Manager agent as well.
For example:
If User belongs to company X then Manager is Test 1
Then determine Asst Ngr also based on same parameters
If User belongs to company X then Asst Manager is Test 2
You need to decide how you determine but eventually you should have 2 BRF+ agents (one for Manager and one for Asst Manager) and you can use them at stage level as mentioned earlier.
Regards,
Madhu.