How to Default Bin Location DFF in Requisition Page based based on Source Subinventory?

CrownCastle is looking to create a DFF(Source Bin Locator) based on Sub Inventory Organization. Currently, I am seeing only these options :

Reference: 

Current Valueset Where Clause:

Where Clause:

ffv.flex_value_set_id = ffvs.flex_value_set_id
AND ffvs.flex_value_set_name = 'LT_BINS'
AND ffv.enabled_flag = 'Y'
and exists
(
select 1
from
inv_item_locations iil
where
1=1
and iil.LOCATOR_NAME = ffv.flex_value
and iil.SUBINVENTORY_CODE = :{PARAMETER} — Need to understand what parameter drives Source Subinventory?
)

Use Case:

We are trying create a Bin Locator DFF based on Source Subinventory. Currently, we are NOT seeing option to pass in Source Subinventory in the WHERE Clause of the query.