If this is what I think it is, this is a Vst3 issue… Not with Cubase, but with some 3rd party plugins not implemented correctly.
I have Vst3 plugins from a couple of other vendors (Boz Digital ++) that behave as you explain. And when opening the plugin editor the bypass is missing.
The same plugins in Vst2 works as expected.
PS. I have contacted Boz Digital Labs, buy yet to receive an answer