Help needed filtering slicers

Hello all,

I have such a table as you can find below:

Table1
id       col1        col2       col3       start       end       counts_of_ids       ranks
a_b                                                 a            b                         10              1
b_c                                                 b            c                         10              2
c_d                                                 c            d                          5               3
...       ...              ...            ...           ...             ...                        ...               ...

Here 'start' and 'end' columns are created in 'edit query' section by splitting the id column by the delimiter "_" which is the foreign key for another table. Here, I would like to add a slicer of 'start' column to my report which should be able to filter my table by the start column. Besides, I also have a dynamic filter connected to ranks column and let me filter top N values. So, My problem here is, I filter my table by this topN filter and it works perfectly. However, I also would like to see filtered results in the 'start' slicer. So, If I have, let's say, 20 rows at all, when I select top 5, I would like to see 5 values in start slicer.

Since, I can not add 2 fields in slicer at once, start slicer shows more values then filtered, because my ranking fails without id information. Could you please show me a way to combine two columns to each other but create a slicer by only the start column out of this combination. 

If I am able to combine id and start columns it works! So I either combine this two columns or filter the slicer by ids but I could not achieve both approaches. 

Thank you very much,

Cheers