Reply To: Delete unused panel items?

In the menu panel for each you can choose “Select All Unused” then remove the ones not used.

Some paragraph styles may be based on others (child styles) or be a base for other styles (parent styles). So you will have to choose None for the replacement style and then tick the Preserve Formatting box.

But you should be able to remove most things using the menu from each panel.

I'd start with Master pages

Then table and cell styles

Then object styles

Then Paragraph Styles

Then Character Styles

Then swatches.