as far as I know, there’s not an existing screen that will allow you to do this. there’s been some thought about making a 3rd party tool to handle this, but i don’t think anyone has actually made such a tool yet. so then i think the only way to do this would be to issue a request directly to the API. would you be interested in doing that? (if so and if you need help with that, are you comfortable with a programming language like R or Python? or else what OS are you using?)
the basic thought process would be that given:
- existing photo ids on obs 111823385 (spider): 188818860,188819896
- existing photo ids on obs 111532888 (liverwort): 188291612,188299523,188299543,188299668
… you would want to make the following API request:
curl "https://api.inaturalist.org/v1/observations/111532888" -X "PUT" -H "Content-Type: application/json" -H "Accept: application/json" -H "Authorization: JWT" -d "{\"local_photos\":{\"111532888\":[188291612,188299523,188299543,188299668,188818860,188819896]}}"
(note that you’ll have to replace “JWT” in the command above with an actual JWT. you can get one by going to https://www.inaturalist.org/users/api_token in your web browser.)