If anyone's familiar with this kind of functionality, how are you
supposed to record future events if you have to work this slider
to make the recording happen and essentially render the VCR
useless for anything else in the meanwhile? The whole thing
seems contingent on your remembering when you set the
programs for.

Exactly. No one has ever made a VCR that allows you to manually record while
the machine is in timer-record mode. You have to switch off timer mode, make
the recording, then turn timer-record back on again.

This does not seem to me to be an unreasonable way of arranging things.