Using GPIO pin as a one bit control register

I had some time to try what I wondered in my post and it did not seem to work.    There may be another combination of settings that works.   I think with the control registers being a limited resource, it would be nice to be able to do this, in particular when you only need one or two bits.   If the fitter could split/share bits in a control register, it would be less of an issue, but that does not seem to be the case.   For example, the ISP component in bidir mode appears to use a single bit control register.    I was working on a design that added logic around it, and needed a couple more bits.   It would have been nice to use a segment of the same register, but there does not seem to be possible.    I am sure there must be some tricks somewhere in the huge pile of PSoC things I do not know...