Its simple: you need to use a keyswitch for guitar - in fl studio (without changing a root nore in settings) create a D2 note and playable note, for example F3. both notes should be played at the same time.
@@Stanislav_Mosin Thank you for the advice but I created a d2 note in the fl studio piano roll and played the f3 note at the same time with it but still no palm mute. What should I do?