There are tutorials on how to visualize source localized differences between two conditions. What if we have 3 conditions and we are interested in any significant effect, for example, Condition 1 is significantly higher from the other 2 Conditions, Condition 2 is significantly lower from the other 2 Conditions, ... etc.
This applies to any calculated signal say power.
I'm open to calculations outside Brainstorm and then use Brainstorm only for visualization.
Also, any references to studies had the same issue.
Unfortunately, Brainstorm does not provide tools for estimating the significance of interactions between multiple parameters, or for one parameter with more than two values.
You can export the values you want to test in various ways and test them with external programs. The best procedure depends on the type of data you want to test, and also then amount of data you have to extract.
If you want to export only one or a few values per file (eg. power at a given frequency or source values for a few scouts or a few sensors), you can select the files you are interested in and run the process "Extract > Extract values". This would export everything to a single file, that you can easily read in Matlab or export to a text or Excel file (popup menu File > Export file).