Scripting: Actions can't have checkboxes

If an Action is checkable, its icon is displayed instead of the checkbox, with a button-like look to indicate whether the Action is checked:
Default icon:

Custom icon:

When an action with an icon is unchecked, it's hard to see that it even can be checked. The default checkbox does a much better job of communicating that an action is checkable.

This only affects scripted actions, as none of the native checkable actions have icons.
Since script authors can simply choose to not assign an icon, it's probably fine that those with custom icons are displayed this way, allowing authors to essentially implement custom toggle styles if they wish. However, there's no way to not have an icon since iconless actions are given the extension icon by default! Therefore, there is no way to display a regular checkbox for a scripted Action.

Possible solutions:

• Do not show the default extension icon on Actions that are checkable
• Make the default extension icon small and have it overlap the corner of the checkbox (and possibly any assigned icon as well).