Hi,
The value in the _vLookupID column is generated by the vLookup script so you cannot use this directly. You can however build this in the WF as the “ID” can be any unique string.
The format can be all alphanumeric characters, and must have this format:
xx:xx
The length of the parts left and right of the colon is not important, but you must ensure this “ID” will be unique within the list.
Hope this helps,
Alexander