How to remove bars from tail end of my beat in B+B editor?

[FridayLights]

Hi guys. I'm trying to make my first song and have run into a very annoying issue that no amount of googling or forum browsing has been able to solve. Suppose I have a beat that looks like this:



And I want to remove the bit that's highlighted in red, every bar following the three sequential kicks. How would I go about doing that?

[musikbear]

Hi guys.

Hi, Welcome to the Forum FridayLights !
Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions

I want to remove the bit that's highlighted in red

Any Beat-track can be changed into a piano-roll pattern.
Right-click you wanted track, and chose option "Open-in-piano-roll"
Here you can manipulate singe notes in your percussion, including removing notes, but OBS! The pattern must fit inside the bar! Otherwise you will have empty time-slots, and that would sound weird (can be hack-repaired, but its fidly so best is to have perfect fit)