If you want to make changes to a dimension or measure that is linked to a master dimension or master measure, you must first unlink it from the master item. The dimension or measure in your visualization is then independent with no connection to the master item in the assets panel.
Unlinking from the properties panel
A linked dimension or measure that is used in a visualization can be unlinked from the properties panel.
Do the following:
The properties panel opens on the right-hand side.
Select the visualization on the sheet.
The properties for the selected visualization are displayed in the properties panel.
Under Data, locate and click the dimension or measure.
A linked dimension or measure is indicated by the symbol .
A dialog is displayed that you are about to unlink from a master item.
The dimension or measure used in the visualization can now be edited and the changes will not affect any other dimensions or measures.