In classical terminology portamento would probably be the most appropriate naming for the effect you wish to notate, and the notation for that is a
slur connecting the notes in the "gliding" range extremities. A curved slur is the most common form of notation:
In some instruments that allow for portamento, like the trombone and timpani, a slur may imply portamento. In other instruments it may have specific meanings (like the bowings in bowed string instruments) or just mean to play legato (like in the piano). [thanks to @leftaroundabout for the improvement of this paragraph].
However I have also seen used an oblique "straight" slur (I'm not sure if it's still called a slur if it is a straight line) to indicate portamento, in situations where the round slur could be misinterpreted as a portamento when it was meant as legato.
The simultaneous use of the slur and "straight" line also can be used (as I understand it is used mostly with bow instruments, as the slur on it's own is used to indicate the intended bowing).
Any way, these are only suggestions. Your piece is specific and uses specific technology that may not be possible to notate (to your satisfaction, as notation is always an aproximation). So you should feel free to adapt, adopt, or develop your own form of notation, as many composers have done.
Just as an example of a possible approach to transcribing a synthesizer piece I include here a few excerpts of a transcription for a Tangerine Dream piece (Choronzon, from the 1981 album Exit). As can seen a combination of music notation, suggestive graphic signs and text indications is used. (I expect the inclusion of these small clips is considered fair use and does not infringe on copyright)