Editor Utility Blueprints
There are many different types of editor utility blueprints. For the case of this feature, we are going to use an AssetActionUtility as our base class.
From the source code, the Asset Action Utility allows us to call a function on our currently selected assets in the content browser. This allows us to include new actions in the right-click submenus if the asset class is valid for our context.
Bulk Reparenting Implementation
Create a 'Editor Utility Blueprint' from the parent class type 'Asset Action Utility'. I named my asset 'ActionUtility_ReparentSelected' but the name is irrelevant to any displayed information.
The implementation of this asset is very simple. In class defaults ensure that this 'Is Action for Blueprints' is true and that supported classes include the Blueprint type. This means all Blueprint assets are supported for bulk reparenting.
Create a function called "Bulk Reparent Blueprint" or whatever you want this function's display name to be. The actual code simply goes over all selected assets, checks them out, and reparents them if possible.
You now should be able to use the bulk reparenting Asset on all blueprint types!
Brief introduction of tooling assets in Unreal and how to create a simple bulk reparenting action.