Show an icon or something to Indicate that a layer has plugin data applied to it and possibly show the plugin data somehow.
Some artboards can have up to 400 elements and some projects up to 10k total elements (see Statistics plugin).
If a user has set any plugin data on a layer it can be hard to find which layer that is when you have 50 layers named something like Rectangle_38.
If the layer showed that plugin data was applied to it that could help the designer see, find and debug plugin settings. If it was able to show them the value of the saved plugin data that would be helpful too.
FYI Many web browsers have something similar to this in their page inspector dialog that shows the cookies that are set and their values.