Hi Peter.
Right now you can only add an action to the context menu by adding to the class side of GTPlayground a method annotated with <playgroundContextMenu> that takes a parameter and returns a list of glamour actions. The parameter will be the actual instance of the playground. You can find an example in #contextMenuBasicActionsFor:
GTPlayground class>>#customActions: aPlayground
^ {
GLMGenericAction new
action: [ self inform: 'action' ];
icon: GLMUIThemeExtraIcons glamorousBrowse;
title: 'Action' }
Indeed we should have a similar option for customizing the buttons from the toolbar.
Cheers,
Andrei