Hello Joshua,
I understand that you are encountering an error when attempting to use the "sliceViewer" function in MATLAB.
I experienced a similar issue while working with the "sliceViewer" function in the MATLAB Live Editor, version R2023b.
I discovered a workaround that involves either explicitly specifying a parent for the "sliceViewer" function or creating a named figure before calling the "sliceViewer" function.
I hope this helps.