Thank you for your help, too! I think I understand now that what you’re showing here:
is changing the item referenced in this key here:
but I’m not sure how your Fotos_Arquivos relates to my data. Do I need to create a whole new data type for these images? Right now the thumbnail image I am saving is a Thumbnail field of my Post data type, so I can’t access that through the Type dropdown as you have done.
Editing to update, I figured it out! I do need to change the Post and access the Thumbnail field through the parameters (thank you Bubble tooltips!)

If you’re able, I’d still like help figuring how to combine calls, so that I can properly provide the source url, and get back a resized, “thumb” (intelligently cropped), 512x512, converted to webp.