Uhm, in what context? Looks like HTML/JS, but why?

in some parts of the game level code like GameMenu.scene.xml and MainMenu.scene.xml and chapterX.xml.... onclick="dosomething" defines what happens when we click on a new chapter, new level, retry button, OCD button and any other buttons. I can't find the place where "dosomething" is defined. (please don't let it be embedded in the game.exe) I think gootool uses this to start a new level.

Yeah, finally figured out what you meant on my way home.
I looked for the definitions myself some time ago and didn't find any. Someone also mentioned that many things like these are indeed defined in the compiled code. :I
Maybe someone here knows for sure...

They are hardcoded. button onclick values:

backtoisland - transition to chapter from level (in-level menu)
continue - hit the first continue handle, launches the flush screen
credits - show the credits screen
doconnect - connect to Internet from wogc
island<n> - transition to chapter from main menu
pl_<level ID> transition to level from chapter
quit - exit the game
restartlevelrightnow - restart level without confirmation (in-level menu)
resumegame - resume game (in-level menu)
showmom - launch MOM or show "come closer" message
showocdcriteria - show ocd (in-level menu)
showselectprofile - show the profile selection screen
showtermsandconditions - show MOM's terms and conditions in wogc
submit_and_flush - second continue handle, does the flush
update_submit_level_stats - toggle "submit scores to leaderboard" (end of level scene)
wogcorp - transition to wogc from main menu
wogcorp_from_island - transition to wogc from chapter
zoomout - transition to main menu from chapter or wogc