Gelix:
I was woundering if can add my own elements that dont disapear when you close the game?
Yes, you need to use a file named autorun.lua in the same folder as the TPT exe. I would strongly advise you to use this nice script manager:
https://powdertoy.co.uk/Discussions/Thread/View.html?Thread=19400
With it, you can download/install scripts and enable/disable scripts from within game (note that disabling a script requires the game to restart).
To use your own scripts with this, you just need to put lua files in the scripts folder, then enable them from the in-game Lua button GUI.