There is a Plex help topic 'Deleting Objects', that provides more details on object deletion.
Here is the help topics snippet:
When you delete an object, you also delete all of its properties and all of the objects that it scopes. Thus deleting one object can result in many other subsidiary objects and triples being deleted as well.
You can delete objects using the Model Editor, the Object Browser, the Variable, Panel, Report Palettes, or the Diagrammer.
To Delete One or More Objects
Select the objects you want to delete.
From the Edit menu, choose Delete Object. In the Object Browser, choose Details from the pop-up menu, then click the Delete Object button on the Name tab of the Details dialog.
A dialog appears, requesting confirmation of your deletion request. In most cases, you can ignore the Ripple Delete check box.
Click OK to proceed with the deletion request.
An additional dialog appears that uses a tree structure to show all the objects and triples that are deleted by your request. All triples across all configurations display. For performance reasons, CA Plex skips this additional dialog if you are deleting more than 2500 objects.
Review the objects displayed and click Yes to confirm the deletion.
E.g. Deleting the 'FieldB' shows the below list of objects having reference to 'FieldB' in local model, so review before deleting. This image is not part of help topic.
if you make a mistake, immediately choose Undo (CTRL+Z) from the Edit menu to reinstate all the objects and triples you just deleted.
Another help topic 'Removing fields and regions':
You can also omit fields and regions through the Variable, Report, and Panel Palettes. To do this, highlight the field or region to be deleted, right-click, and select the Remove option. You can also press Ctrl+R. You can only delete fields or regions that have been added through triples created at the current level of inheritance. If you select one or more invalid fields, the Remove option is disabled.
Note: No fields or regions are deleted from the local model when they are removed from a palette; only the triples associated with their addition to the palette are deleted from the model.