When you click the note, it opens up an interface immediately. Once the note is closed, it queues up a stackable interface (like a prayer). This is useful, because if you spam click the scrawled note, you'll always have exactly 1 stackable interface queued. This means you'll always be holding the wave end with exactly one stackable interface.
To force wave ends: simply spam left click the note and hold the ESC key with the option for ESC to close interfaces enabled. Once the NPCs are all dead, stop clicking the note. The ESC key is held down to automatically close the first interface and thus not obstruct your visibility. You can also walk while holding the wave end if you click to move during the first interface.
Note: this stackable interface is low priority, and pops in the order it is queued with other low priority stackable interfaces (i.e. prayers, fixed device, etc.). To do the egg duping on the queen wave, you can't use low priority stackable interfaces. You should use an animation stall such as mind shield to dupe eggs (which ofc can be chained into the translated note if you want).