Go to a database table and click the Edit icon. It takes you to a separate page where you can edit the row. If you have set up relationships in PMA (the "foreign key" thing for MyISAM) it displays a link to the right of the fields to "browse foreign values".
However, on the table view if you tick several rows and click the Edit icon at the bottom of the page, it pops up with the quick-edit modal window* but the icon to browse foreign values is not there! Although if there are only a few foreign values, it does show the <select> element.
* I honestly have no idea why it shows here and not for the other situation. Logically, a quick-edit would be the exact opposite, showing for a single field but not for multiple. Regardless, have some consistency and use the modal boxes for everything.