Save these as bookmarks, then activate when on an appropriate page to trigger their effect:
[RDFa to JSON-LD] Extracts RDFa from the current page and displays it as a JSON-LD serialization (uses RDFa to JSON-LD).
[Toggle RDFa.CSS] Toggles the RDFa.CSS for a page (applies a special style which highlights elements using RDFa attributes).
[Convert Schema.org microdata examples to RDFa] If you like schema.org, but prefer RDFa over microdata, use this bookmarklet on the schema.org pages.
Depending on what your browser supports, either:
A) right-click and add as bookmark; or
B) drag the link to e.g. a bookmark toolbar; or
C) right-click, copy the link address, then create a new bookmark and paste the link there (it should begin with "javascript:").