In libreoffice-7.2.1.2, it isn't possible to change the line spacing using the mouse from either the icon on the toolbar or the Styles -> Edit Styles menu. I suspect this bug is probably related to bug #258703 as from the Edit Styles dialog, I can change the line spacing using the arrow keys. It seems like some mouse events aren't getting processed correctly. As a note, this bug does not exist in the libreoffice6-6.4.7_15 package.