Will it be possible to access more than one file in a session?

I tried an 'attach', but B4S (Browser for SQLite) seems not to support it. Perhaps in a future version?
Standard one can attach nine more databases and even 124 with runtime-options.

Ref: http://www.sqlite.org/limits.html#max_attached

I get
cannot ATTACH database within transaction: attach 'file:../db/main.sqlite:mode-ro' as dd;
I wrote
attach 'file:../db/main.sqlite?mode=ro' as dd;