I create a line chart from a set of data, eg A1 to R100 but the width of the lines for each row of data are too thick. I therefore have to select and change each line individually, and have to do so for any new rows added. You assume that applying a template will change the format of any new charts, but it only applies to the data range the template was created on. So after applying a template, any new lines still have to be changed manually, so I am back to square one.

What I need is for the default settings to be changed, so all future chart lines are thinner, whether you are creating new charts or adding to charts already created. I cannot see anything under File/options.