Hello!
kkors Is there a way to automatically import new data from a cryptpad form to an existing cryptpad spreadsheet?
Sadly no. We would need to find a way to import data into an existing spreadsheet, which isn't supported by OnlyOffice itself.
A spreadsheet content isn't simply text, it's a very complex type of files. We'd have to reconcile changes, merge them, etc.
kkors And if there is no automated solution, then is it possible to manually import new data from a form to an existing spreadsheet?
Yes, by doing what you described in your message right after your question.
kkors Is there a more efficient way to do this? Either through a cryptpad feature or through a workaround.
Not at this time sadly.