@Reinaldo,
When you say participants, let us take two of your tables ( say Table 1 and Table 2) - are you saying that Table 1 and Table 2 have the same # of columns and you would like to join them ? And when you join how would you like to perform the join :
1. You can match columns - so if Table 1 & Table 2 have a column named "Age" then your resultant table will also have one column "Age" , but with all the rows in both the tables
2. You can do a cartesian join
3. Join By Row Number ?
Yes it is possible to perform Joins using the menu . Select one of your tables and navigate to Tables == > Join . The Join menu should look like this , now within this - depending on how you perform the join, your results will vary. I am presuming you want to select "By Matching Columns". Try that and see if that gives you what you are after, else please provide clear examples or screenshots.
Best
Uday