there are 2 usb slots, u can plug in 2 ext hdd; u also have the int hdd inside.

to copy/move files among the 3, u need a file manager.

just go to playstore and install one that u like - X-plore, Amaze, File Commander, Asus File manager.

all of the have file transfer capability.

doesn't look like himedia will have anything good and new coming soon.
side info, this AM6 Plus looks good, reviewed to be better than predecessors AM6 and AM6 Pro.

will explore further if it is worth acquiring... suppose to have dolby vision, Atmos/DTSX capabilities, root switch.

Ugoos AM6 Plus, AML S922XJ, 4+32GB, Android9, Hexacore 2.2ghz... about $140 or rm6xx.

https://ugoos.com/
https://tvboxstop.com/2020-tv-boxes/ugoos-a...-2-2ghz-tv-box/
https://www.youtube.com/watch?v=eH_cLjblgds

according to the review, yes. DV+atmos playback.

not too sure as i had never tried it but from reviews, many new boxes can playback DV.
and they can passthru atmos too... but many cannot do ddtruehd, dtshdma.
of course, these are w/o DRM support, will not do atmos or HD for netflix.

here, another comment:
this box hasn't reached local online stores yet... will wait a bit.

of course u do, me too.

and bdmv full menu, autoframe rate, quality video+audio engines, root switch (to use astrogo, unifiplaytv).

which is why it is so blardy hard to find one!

Q10pro has been excellent for last 5 years; just that it can't do DV, getting old... android7.0...
i will be following this ugoos am6plus and minix u22xj, see if any one these will meet my requirements.