By default two sets of symbols for significance test visualization are available. You can select between +/- and ↓/↑ to indicate if a value is significant or not. The +/- symbols can, for example, be used when comparing segments (age groups, stores, gender, countries etc.) while the other set of symbols (↓/↑) can be used when comparing time intervals (weeks, months etc.)
The symbols are defined in the Project settings page. The image below shows the Project settings page. You can define the two sets of symbols in the highlighted section.
The image below shows the setup of a chart and a table. Here, you can select which set to be used.
The Symbols dropdown list only appears if “Symbols” is selected in the Visualization type list.