Define all [Tray]Current[Whatever] as 0 or something else. e.g.
You only want to do this if you actually use the strings $[Tray]Current[Whatever]$ in your rc files. You only have to do this so that litestep won't give you error messages about these being undefined before the module is actually loaded to provide these evars.

If you use mzscript or xlabel or skinbox or another module that has an escape code for '$' then of course you do not have to make these dummy variables. You can use in your scripts %#[Tray]Current[Whatever]%# which at runtime the %# get substituted with $.