I created test calibration models for transparent PLA & PETG.
You use this as a starting point to t7 e your own filament to get it as best as you can without resorting to sanding, polishing and other non-printing techniques.
The most important thing to remember is the word transparent is very misleading, you are working with translucency and the degree of success comes from how translucent.
No current FDM can achieve transparent.