Describe how you implement the many to many relationship. Usually this is done with a third, join table. Is this how you've done it?
Once you describe your releationship we should be able to help you do what you need pretty easily.
Yes! I use a join table!
Create a layout that uses the Join table as your underlying table.
Place the fields from exhibitions and paintings that you want to see in your report on this layout.
Perform a find to find all records for a given exhibition and you'll get your report listing all the paintings for a given exhibition.
Perform a find to find all records for a given painting and you'll get your report listing all the exhibitions for a given painting.
If you don't know how to create sub summary parts, you'll probably want to learn how to add those to your report as well. (Sub-summary parts allow you to group records under subheadings.)
This is exactly what I needed.
I made a sub-summary report in list-view and made a script for that as well. From a record I can go directly into the report that shows all the data fromthe portal.
(But why do many insist on the opinion that you cannot print portals?)
In your case you didn't print a portal. You printed a list view layout with sub summary parts. This is usually the better way to print data that has been entered into related tables via a portal. It gives you much more flexibility.
Actually, One of my databases prints invoices from a layout that has a portal on it. It's been doing that since it was an FMP 3 or 4 database. You can print layouts that display data in portals, IF you understand their limitations and can work within them.
The most significant reason people advise you not to print from a portal layout is that if your portal has to scroll to display all the related records, printing that layout won't show all the rows.
In the case of my invoices, the data entry screens use nonscrolling portals with the same number of rows as my output layout. Since the user can never enter more rows than are visible in the layout, I can print my invoices using a portal in the layout.