Excel Waring / Error:
Complex formatting that is applied to the selected chart may take a while to display.Description:
In MS Excel, while changing the color, line width, line format (dashed,round,dash dot etc) , a warning will be showed as follows."Complex formatting that is applied to the selected chart may take a while to display"
If you continue to change the format, ignoring the warning, then the graphs will load very slowly each and every time you update a change in the graph. Overall speed performace of the excel file will be reduced.
Sometimes, if you change a color of the line or increase the text inside the graph, then it will not get referenced immediately. You need to click somewhere else on the sheet or some other graph to see the update you have done recently.
Solution:
So, the best practice is to leave the graphs with the default formatting. Make the changes in line formatting of the graphs only if it is necessary.You can revert the changes made in the graph by applying another chart style by double clicking the chart and selecting a chart style in Design → Char Tools