Duplicates of the same filter in a single pipeline cause usability issues

[mmarineBlueQuartz]

This issue refers to duplicates of the same filter not as two of filter X or the result of copy pasting a filter. Instead, it appears that two copies of the same filter pointer are existing in the same pipeline at the same time.

Deleting the second instance of the filter by pipeline instance instead removes the first one from the pipeline. Dragging either only moves the first occurring filter. Deleting either filter only removes the first filter, and the other one can be infinitely deleted without removing it from the UI. Each of these delete actions can be undone to reinsert the not-deleted filter back into the pipeline at the same index. Only one of these new copies can be moved or deleted, but it can be done through any of the copies displayed in the UI.

To duplicate this, drag a filter from one pipeline to another. Undo the move on the initial pipeline, and drag the moved filter back in. Every copy shows up as having an error, but none are added to Pipeline Issues. This is still true after undoing a several deletes of the last duplicate filter (that is never actually removed), resulting in multiple copies of the filter.

This also points to potential issues where the same filter in two pipelines can cause issues where signals cross pipelines, and parameter widgets are used to update values while the filter is being executed in another pipeline.