Hello Samuel
I have found a solution. It is a bit unconventional, but it works.

Assuming that my assumption is correct that Dataflex cannot handle 3-table views, I have thought about how to work around this problem.

This is the working solution:
View1 = Table1 + Table2
View2 = View1 + Table3

View2 is then included as a table in Dataflex.
Strange, but it works.

Many thanks for your effort