With split panes, toolbar action apply to the selected / active editor

[bric3]

Suppose two diagrams are displayed side-to-side. Eg

Here, the right editor is selected (notice the blue line on the editor tab).

When toolbar icon is interacted on the right editor, the action will apply on the left editor which is the selected editor.

Either the toolbar should be disabled on non selected editor, or the true matching editor should be selected.