Text position at the beginning of the line

[David_Schumacher]

Hi, how can i write the “Polka” text at that position?

[Spielmann_M]

The simplest way is to name the player (or instrument) and display the player name (or instrument name).
Depending on the context, this may have undesirable side effects; there are probably more elegant solutions.

[asherber]

You can do it with staff or system text above the first note, and an appropriately defined paragraph style.