Excel Power Query - One to many and other way round

I had a list of unicorns downloaded from internet as shown below. The Cat1 is categories column. 

Figure 1

So, for every unicorn (Company), you have one or many select investors. 

Step 1:

Using power query in Excel 2016, I filtered the list to show Indian unicorns (16 of them). This was a fairly simple operation. 

Step 2:

Then again using power query I transformed the column containing select investors (many in one cell) in to multiple rows. I got a list of every Indian unicorn against the every select investor. The total number of rows grew to become 46.

Step 3:

Further I grouped all unicorn companies on select investors to know all the Indian unicorns they have invested. But for that I had to write a small custom function to combine all the unicorns as one list against every investor from select investor column. Then the list was put in column named Custom. Now we know each investor and Indian unicorns it is investing in as shown below. 

Figure 2

So, to conclude from unicorn company with its multiple investing firms; we now have investing firm and multiple unicorns companies it is investing in.  

This kind of requirement comes often with different contexts. I am new to power query and finding its usefulness as I could do the above in minutes. Next I want to do similar output using python.