Hi @Anonymous,
Could you please share a bit more about the Markers property within the Pie Chart on your side?
I could not find the Markers property within the Pie Chart control. I only find the Markers property within the Column Chart control and the Line Chart column. Do you mean that you want to view the markers in the Column Chart control as percentage?
If you want to view the markers in the Column Chart control as percentages, based on the thread that you provided, I have made a test on my side, I think the Text function may not achieve your needs.
As an alternative solution, I think Text function toggle with the MakerSuffix property of the Column Chart could achieve your needs. I have made a test on my side, please take a try with the following workaround:

Set the Items property of the Column Chart control to following:
AddColumns(
ColumnChartSample,
"Percentage",
Text(Area/Sum(ColumnChartSample,Area)*100,"[$-en-US]#.00")
)
Set the MarkerSuffix property of the Column Chart control to following:
"%"
Set the Series1 property to of the Column Chart control to Percentage column.
In addition, if you want to view the markers in the Line Chart control as percentages, I have made a test, I afraid that there is no way to achieve your needs in PowerApps currently.
Best regards,
Kris