Love this whole series! What is that background tho that looks like a real page on the score?

I think a more standard way to show the open hi-hat is to put a circle above it. I would recommend that you select "Open Hi-hat" under "Edit drum set" and set "Staff line" to -1. You can then manually add "Open" in the Articulation palette. As a drummer, I find it very disappointing that Musescore doesn't take the most standard way to showcase the Open Hi-hat.

Great video! It would be nice to have some sort of Muse Drumset with built-in velocity changes depending on the time signature. Loving the series!

Personally, I prefer to write drum parts with slashes throughout instead of slashes followed by repeat bars. The repeat bars say “do exactly what you just did”, which is more at home in orchestras and concert bands where the percussion is fully written out. However, bars with slashes say “do whatever you want as long as it follows these guidelines”, which is far more in-character for jazz drummers. In practice, the distinction between these two placeholders is effectively useless, so mixing them like this will confuse the drummer more than it helps them.

The laggy note input sound might just be your computer/musescore struggling to refactor the playback with such a large and complex sheet. I’ve not experienced it myself but I’ve also not gone over eight instruments or to the same level of detail.

The swing in MuseScore should really be made to automatically set to 67%, the ratio of 2:1, (2/3 in fraction form) as close to “two parts first note one part second note” as you can get)

A lot of the time just saving the score will help MuseScore “catch up” and stop being laggy. I noticed you weren’t saving very often so I think that might be the issue

are you able to add other instruments