Yeah Advanced URI supports appending to a random file you give it in the URL (you can see all the options here ) The best would be to try on PC to find the correct working syntax for your inbox note then copy it on the scene tasks.
If you click on Scenes in Tasker and select Obsidian input then click the Save button it will open the settings then Tasks → Browse URL is where you adjust with the new settings you want. Just remember to re-add the variables (at least the %OBS_CONTENT since it’s the formatted content you typed into the field).
Sadly there’s no formatting or anything (other than URL encoding) so if you want all items to be a list you need to add a - in front. It just takes everything you type exactly as is and append it to the note.