Acciaccatura Before the Beat
BEFORE READING: for some reason, after opening the plugin a certain amount of times (i.e. closing and running another instance) it crashes musescore. For that alone, try to not open many instances; I've no idea why this happens, so, make sure to save your score if you plan on running many instances.
Since it's a dock, it will hopefully not cause much trouble. Apologies for this.
In some styles of music (heard here: https://youtu.be/C8KsMCrq3jU), some kinds of drum notation (heard here: https://youtu.be/WWursLMsEHU), and according to each composer's taste, acciaccaturas (or appoggiaturas) are played before the beat.
The default playback in musescore happens on the beat, and its length is not easily editable without plugins (see Articulation and Ornamentation Control).
This plugin is a modified version of the appoggiatura plugin made by Bernard Greenberg, a bunch of code from the DockArticulate plugin and another bunch from Kate Dudek's "Pipeband - On The Beat" Plugin for Bagpipe Playback Correction.
The musescore link/file demonstrates the extent of what this plugin can do, so it could be useful for things like simple two notes acciaccaturas or long phrases in a cadenza.
To use the plugin: make a selection, it doesn't matter if it has notes without a grace note, just make sure your selection has at least one note with a grace note otherwise it won't do anything. The main note length value is how long the note is, just like the piano roll; the separation value is how much the grace note(s) play before the beat, distributing them evenly.
The changes will only affect notes with a grace note (also make sure to leave the main note length at 0 or 1000 or 950 if you want to preserve its initial value. This varies too, since staccatos are 500, so I'd reccomend looking into the piano roll if the main note has an articulation).