how do I detect deletion of a custom block(not the definition) and get the parameters for it?
You can use the when [anything V] is edited ((data)) @< block to detect custom block deletions, however since it's when anything is edited, you have to filter out the (data) variable. It should look like this when a block is deleted
As you can see, the block label is there with underscores as the input placeholder. Unfortunately, this doesn't tell you what the input names are.
the custom block instance, do I need to pare the xml?