An issue I've had switching to Aerospace is that typing # (on a mac) causes me to switch to workspace 3:

[mode.main.binding]
    alt-3 = 'workspace 3'

A fix I came across was to define an empty binding mode. When switching to a new binding mode, all the previous bindings are disabled in favour of the new bindings, allowing me to type #.

To get this working I mapped Option + Backspace in the main and new mode to toggle between them:

[mode.main.binding]
    alt-backspace = 'mode hash'
[mode.hash.binding]
    alt-backspace = 'mode main'

I think this is currently the best solution but it would be nice to map the left and right modifier keys separately.