- Open the relationship view: CTRL+SHIFT+2
- Select all elements on your diagram using the mouse and dragging a selection box around them (Ctrl + A does not work in this tip). Easiest way is to zoom out until the whole diagram is visible.
- This displays the Relationships dialog where you should see all the relationships for your diagram.
- Select one or more relationships in this dialog. Here you can use CTRL+A as you like
- Right-click and select Appearance… to change the width / colour of all selected relationships.
- Right-click and select Line Style to change the line style of all selected relationships.
Tested using Enterprise Architect 13
The original tip comes from: http://dthomas-software.co.uk/sparx-enterprise-architect-tip-of-the-month/