Undo CSR Hall effects

In the Master Control Strip of the mixer I select CSR Hall.
In "Send" mode I select Small Concert Hall. Perhaps I should use "Insert" mode, but there is no Small Concert Hall effect in that mode.
Once an effect is selected, I cannot undo it. I tried the "Delete" button on the effects rack, but to no avail.
Is there another way to undo the effects, besides closing the file w/o saving changes?
Thanks!
In "Send" mode I select Small Concert Hall. Perhaps I should use "Insert" mode, but there is no Small Concert Hall effect in that mode.
Once an effect is selected, I cannot undo it. I tried the "Delete" button on the effects rack, but to no avail.
Is there another way to undo the effects, besides closing the file w/o saving changes?
Thanks!