I am really sorry, TBOne.
You can view the font
here, in the Exodia folder.
I built the lookup table like this :
Elements menu > Font Info > Lookups > GSUB tab >
Add Lookup,
Type - Ligature Substitution,
Feature - cjct (Conjunct Forms), Scripts - DFLT{dflt} beng{dflt} latn{dflt}
Lookup Name - 'cjct' Conjunct Forms lookup 0
I then added a new Encoding Slot : Encoding Menu > Add Encoding Slots > 1 slot, renamed it uni0995_uni09CD_uni09B7.cjct and imported the glyph image there.
Then I added the subtable by clicking Add Subtable and added the data of substitution there.
Ligature Name : uni0995_uni09CD_uni09B7.cjct
Source Glyph Names : uni0995(ক) uni09CD(্) uni09B7(ষ)
It works when I hover the pointer above the entry in the subtable.
Then I exported it by File menu > Generate Fonts. I tried both OTF and TTF, but without any results.