Libreelec beautifully designed as an open source just enough OS (JeOS) to host kodi so it is up to kodi and streaming services to brings any specific feature to consumer, unfortunately kodi for now rely on its horrible and ugly addons to brings streaming videos services to consumer. there is YouTube addons which you can find in official repository but in no way it comparable to official app both in functional and ease of use. for netflix there is no official way to watch it in Libreelec but there is hack that sooner or later stop working. this situation will remain the same until the the stream services bring their apps to linux or kodi which in very unlikely our Libreelec developer do somethings new for example add android subsystem in Libreelec to run certain android streaming apps even if Libreelec run android apps DRM may cause so much trouble. so i recommend you for your offline music and video collection use kodi and for access to streaming services use its official platform which is android tv(nvidia shield), apple tv os(apple tv 4k), xbox and ....... .

You can make your own youtube video addon to play your playlists from kodi..it's not that hard really..there are lots of tutorials online...a good example is youtube kids addon for kodi...if you look inside it in the resources folder you ll see how it's done

To make your own playlist that works with kodi your playlist has to look something like this

#EXTCPlayListM3U::M3U

#EXTINF:0,Shakira - Trap (Official Video) ft. Maluma
plugin://plugin.video.youtube/play/?video_id=zkG4Xpz6t68

#EXTINF:0,DeMarcus Cousins Out for Season, Pelicans Defeat Rockets in Clutch! 2017-18 Season
plugin://plugin.video.youtube/play/?video_id=8MfSVTHqNHU

Edit your playlist in a text editor like Notepad++ and save it as "nameofyourplaylist.m3u"

Quote from Sirius

How playlist can be uploaded?

Not sure what you mean uploaded?But if you want to upload it online to share it you can use something like pastebin..

In kodi you just put the playlist in the video playlist folder and browse to it or you can use any addon you want that plays playlists from youtube addon..

Not sure what kind of box you have...if you have your own playlists on your youtube account you can access them either from within kodi youtube addon after you log in with your youtube account or with the youtube app on your box if you r getting something android..can't help you much about how to move them to your box if I dont know what box you have but usb way would work with anything having a usb..