How to find a duplicate formula?
Log
Previous:
File: /data/Daz 3D/Genesis 8/Female/Morphs/Angel - Wings/Youth Muffin/Youth Muffin Lower Arms.dsf
Owner: Genesis8Female
Input URI: Genesis8Female:/data/Daz%203D/Genesis%208/Female/Morphs/Angel%20-%20Wings/Youth%20Muffin/Youth%20Muffin%20Lower%20Arms.dsf#Youth%20Muffin%20Lower%20Arms?value
Input: Youth Muffin Lower Arms
Output URI: lThigh:/data/DAZ%203D/Genesis%208/Female/Genesis8Female.dsf#lThigh?end_point/x
Output: xEnd
Duplicate:
File: /data/Daz 3D/Genesis 8/Female/Morphs/Angel - Wings/Youth Muffin/Youth Muffin Lower Arms.dsf
Owner: Genesis8Female
Input URI: Genesis8Female:/data/Daz%203D/Genesis%208/Female/Morphs/Angel%20-%20Wings/Youth%20Muffin/Youth%20Muffin%20Lower%20Arms.dsf#Youth%20Muffin%20Lower%20Arms?value
Input: Youth Muffin Lower Arms
Output URI: lThigh:/data/DAZ%203D/Genesis%208/Female/Genesis8Female.dsf#lThigh?end_point/x
Output: xEnd
In paths
/data/Daz 3D/Genesis 8/Female/Morphs/Angel - Wings/Youth Muffin/Youth Muffin Lower Arms.dsf
/data/Daz 3D/Genesis 8/Female/Morphs/Angel - Wings/Youth Muffin/Youth Muffin Lower Arms.dsf
there is not a single difference.
I don't understand how to find a duplicate formula?

Comments
There're two typical cases in terms of duplicate formula error: 1) Two or more Modifier assets (DSF files) have the very same URI ID; 2) Two or more very same URI formulae are saved within one Modifier asset.
The case you have is the latter. You can simply open Youth Muffin Lower Arms.dsf file with Notepad++, delete the coding blocks of the duplicate formula(e), i.e.
Search by: lThigh:/data/DAZ%203D/Genesis%208/Female/Genesis8Female.dsf#lThigh?end_point/x You should be able to locate two lines, then delete one coding block of them, starting from { to },
Save the DSF file. Reload G8F.