Does anyone have more information about this tags?

Those tags (Marked, PlayCount, LastPlayed, SkipCount) are special, in that they live in a read-write disc area on the player (the "dynamic data" area), rather than in the *1 files. At about line 980 of Emptool's playerdb.cpp, you can see them being read out of the binary structure...

How can I set these tags using emptool?

...unfortunately, nothing in Emptool seems to be writing them back to the dynamic data area (instances of those tags in the *1 files are ignored). This is a bug in Emptool.

Incidentally, SkipCount isn't implemented on the player either,

Peter