A .inline file extension is related to the Base64-encoded inline image format.
INLINE file extension - Base64-encoded inline image
What is inline file? How to open inline files?
The inline file extension is used for the Base64 encoded inline image format.
Most likely some old format without support from developer or producer. No further information could be found.
This inline file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.