It seems like you're being careful about this; which is good.

"Never trust a truss" is what many firefighters say. When any of the support
members of the truss are compromised the strength of the entire truss is
compromised.

Trying to build attic space in a web of truss supports isn't going to be
easy. You'd probably have a safer project if you just put your shelving
boards in the spaces on the trusses where possible. You don't want to start
cutting on any truss. I believe there are issues with doing anything to stop
the flexing of the bottom member of the truss (probably the ceiling joists
for you). There needs to be some room for movement with temp and humidity
fluctuations.