What is your current rclone version (output from rclone version)?

1.54

What problem are you are trying to solve?

Since various cloud storage providers limit upload speed per upload stream (not total for the account), you can speed up large file transfers by multi threading chunks instead of going one by one.

How do you think rclone should be changed to solve that?

Multi thread chunker to upload multiple parts at once instead of part by part 1 by 1 for large files.

This is a long-term project.
Blocks on #4798