You seem to have Loop source turned on in the Properties. Cool. Now, before you add that fill on bar 4, GLUE your MIDI item, so it becomes one item. In that case, when you add the fill in bar 4, it will only be added there.
Alternatively, you can split the MIDI item at the beginning of bar 4, add the fill, and then go about doing the rest of the drum track.
(And you can delete your posts, press Edit, and then Delete.
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