First of all it depends on what operating system you are using to answer what file transfer tool to use.
In a real world complex file system in a computer I don’t see a terminal based user interface meaningful. A 64-bit long file address takes ages to manually write enough times to have it correct without “the file doesn’t exist, check spelling” errors.
On Ubuntu I find Filezilla good enough.
But on windows, I doubt anything is easier than WinSCP. You just log on to the router and open in the file tree the folder you want to add something to in the router and then drag whatever you want from anywhere you want from the HDD in Windows and drop it in WinSCP and the job is done. And then you open the pre connected Putty from WinSCP if you want to run some commands on the router.