Filter tables without relationships

I'm not sure I understand what you need well but It looks like you don't want to filter your source and destination tables manually. But you want to get them filtered based on a filter applied to ProdStep1 table.

Then you probably don't need Source and Destination tables at all. Use your ProdStep* tables.

Let's say you have a filter applied to ProdStep1 table. And it has relationships with ProdStep2 and ProdStep3 and ProdStep4. So these 3 tables are fltered by the filter applied to ProdStep1.  I will use only 3 tables in my example:

My 'All Products' table has 2 columns and (distinct number of products) * (distinct number of products) rows (10K rows for 100 products). For each ID in Column 1 there is a list of all IDs in Column 2.



Now this measure:

Measure := 
VAR _source =
    SELECTEDVALUE ( 'All Products'[Column1] )
VAR _destination =
    SELECTEDVALUE ( 'All Products'[Column2] )
RETURN
    IF (
        AND (
            _source IN VALUES ( Table01[Column1] ),
            _destination
                IN SELECTCOLUMNS (
                    FILTER ( Table02, Table02[Column2] = _source ),
                    "id", Table02[Column1]
                )
        )
            || AND (
                _source IN VALUES ( Table02[Column1] ),
                _destination
                    IN SELECTCOLUMNS (
                        FILTER ( Table03, Table03[Column2] = _source ),
                        "id", Table03[Column1]
                    )
            ),
        1,
        BLANK ()
    )

 (i'm using 1 as a value so all connections have the same width)

will show me my multiple steps process for the selected items in the first table:



just add one more OR ( || ) to add one more step