Taking inspiration from the excellent Hi Notch! by @MStankiewiczOfficial but wanting different buttons, triggers and actions, I used one of the floating menus from Hi Notch! as a template to create my own custom notch floating menu.
However, the action "Show Control Centre" is causing issues, and without fail causes the beachball effect. If I click on the Control Centre menu item, the computer slows down, the beachball appears, and about 5-10 seconds later control centre shows up. Occasionally even the haptic feedback of the trackpad freezes up. Tried restarting BTT but to no avail.
I wasn't sure if it was the floating menu aspect causing the issue, so checked using a trackpad gesture to Show Control Centre but it also has the same effect, so there is something up with this Action.
(MacBook Air M2, macOS Sonoma 14.5)