tried doing that, but that doesn't helps, as the grouping of account is should be done before ranking them.
that means, there are many entries for 1 account and ranking should be done in a way that it should club those accounts first and summarize it based on TER value and then rank it.
So here's what i did, i grouped the the table using edit query, and the group by transformation as shown below.
Now , on the data modelling section , created two column as below
Rank= IF([AccountSegment]="Core",RANKX('Account Grouped',[FYTD]))
categorize = SWITCH(TRUE(),[RANK]>25, "Remainder",
[RANK]>10, "Next 15 Core",
[RANK]>0, "Top 10 Core",
Now use this categorize column to create the visual.
Hope this servers your need.