Is supplicating on Laylat al-Qadr with "O Allah, indeed You are Pardoning, You love pardon, so pardon me" done by frequently repeating it with the tongue or by observing the etiquette of supplication?

The etiquettes of supplication are desirable, not obligatory. They are not a condition for the supplication to be answered, nor do they prevent it from being answered if they are not observed. One should frequently recite the supplication: "O Allah, You are the Forgiving, You love forgiveness, so forgive me" on Laylat al-Qadr, even if the supplicant does not adhere to the etiquettes of supplication. Similarly, seeking forgiveness is encouraged in abundance without requiring the observance of supplication etiquettes. The Prophet (peace be upon him) used to seek forgiveness a hundred times in a single sitting, saying: "My Lord, forgive me and accept my repentance, for indeed You are the Oft-Forgiving, the Most Merciful," without it being narrated that he observed specific etiquettes in that situation.