Seems like resume interface is on hold until a framework decision happens.
However, I had same issue with multiple 120GB to 500GB files I wanted to sync to Google drive. Even over a solid connection, after days of uploading, something always killed the connection.
I ended up tracking down the rclone beta with resumable chunks interface. Once you configure a chunker drive, running the beta will automatically start sending chunked data. In my configuration, I changed the chunk size to 2GB since my files are very large. A downside is that files stored on Google will appear as multiple parts that are useless without being reassembled on download by rclone. Fortunately, starting rclone with the ncdu option lets you manage your remote storage with all chunks combined into their original single files.
I wanted to use the rclone sync option, but there was a minor bug. So if you don't want to use xargs, find, or a script to run rclone on single files, you'll need to fix the bug by getting the golang development environment and the rclone resume branch from github. You'll also need a tiny diff available from issue 87. Then like:
git clone --branch resume --single-branch https://github.com/rclone/rclone
git apply __replace_this_with_the_path_to_the_unzipped_diff_file__
You might need to do other things besides the above in your environment.. but that's the general idea.
When you get the beta rclone running, you can shut down your computer during an upload and when you turn it back on, running rclone will restart from the current chunk. With sync mode, rclone might even start on a different file, but when it gets back to the interrupted file it will not restart the entire file, just the chunk it was working on. Even if you have multiple internet failures that result in different files starting each time, each file will still only restart the chunk that was active for it during the interruption.
Don't try to setup a root systemd service for rclone. Setup a local user systemd timer so access to rclone cache and config don't cause trouble.
I have to admit that I'm really thrilled with this. Thanks so much to everyone working on rclone.