Hi @Farrah24 ,
Here I suggest you to create a measure and add this measure as a visual level filter in your line chart. In my sample, I create a percentage slicer by what if parameter.
VAR _PERCENTAGE =
DIVIDE ( SELECTEDVALUE ( Percentage[Percentage] ), 100 )
VAR _MAXINDEX =
CALCULATE ( MAX ( 'Table'[Index] ), ALL ( 'Table' ) )
VAR _ROUNDUP =
ROUNDUP ( _MAXINDEX * _PERCENTAGE, 0 )
VAR _RESULT =
IF ( MAX ( 'Table'[Index] ) >= _MAXINDEX - _ROUNDUP, 1, 0 )
Result is as below.
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.