URL hacking for the rescue! You can append
&list=UL to the end of a video URL from that user.
So, if you have:
it should become:
^ right here
You could also add something like this to your bookmark and simply click on it:
Select it then drag and drop it on your bookmarks.
I couldn't figure out how to properly
href it here in stackexchange! :(
Now, there is an issue! It's got a weird behaviour as dear @burtek brought to my attention on the comments. In my instance here, with Valentina Lisitsa, she got 272 videos right now, but it won't ever show more than 99 on the list. And it seems like it's ordered from oldest to newest, so if you want to play all videos you rather start with the user's first video. In her case, this is it:
From there you can leave it playing and it will play all her videos. The current video will always try to be in position #20 of the list, showing 19 previous ones and 79 next ones.