Improve feedback on impossible actions

[zaguiini]

What problem does this address?

Sometimes the user is attempting to perform an impossible action (e.g. trying to add two blocks that can't live together, or trying to nest un-nestable blocks) and there's no feedback at all that the action cannot be done.

That happens on both list view and the editor itself.

What is your proposed solution?

• Change the cursor to not-allowed;
• Change the color of the drop space from blue to red.

[talldan]

@zaguiini Is this for drag and drop? If so, I think there's another request for such a feature - #24174, and this can probably be closed as a duplicate.

[github-actions]

Help us move this issue forward. This issue is being marked stale since it has no activity after 15 days of requesting more information. Please add info requested so we can help move the issue forward. Note: The triage policy is to close stale issues that need more info and no response after 2 weeks.

[zaguiini]

Yep @talldan looks like a duplicate. Closing this one.