I think it's allowed to have same name resources in two different places, though I don't know how that should be handled in UI so that it's not confusing for the user.

Maybe some kind of adorner telling user that this resource can't be bound to the property (since there's a same-named resource that would be used instead).

Thanks Dario, maybe I wasn't clear enough with the problem: If you assign a resouce with the same name in a different dictionary, Studio only applies the first one, so for example:

1. Create a brush resource
2. Create a merged dictionary
3. Create another brush resource with the new dictionary selected
4. You've got two different brushes with the same name (e.g. SolidColorBrush.001)
5. Create an element and apply the first resource you created
6. Then try to change it to the second resource, either drag and dropping it or using the Resource expander.
   You'll discover that it's not updating.

Now that I thought a little about this, you're right. It's working as expected, so there's this solutions, change the suffix for the newly created resources in merged dictionaries or show either a toast or dialog when trying to use a resource with the same name.
We should close this bug.

Unfortunately, we have the same problem here: https://youtu.be/j-TOPx6B0AI?feature=shared&t=527

This is working now, should be closed