A little clarity to add is once you can climb V4 consistently then you could start worrying about things like actually incorporating hamgboarding but the sub max training you could start doing very early.

To agree with other posters here V4 is the first plateau you tend to hit a new climber, then getting to consistent V6; and do not rush into heavy ass hangboarding too soon. Tendons develop much slower than muscle and going too hard too fast will just lead to you hurting yourself and being injured for long periods of time.

Starting with sub max hangs and working into just bodyweight would be good starting goals to supplement your climbing. I tend to follow the advice from Beastmaking in the “little and often” mentality now; I do 2 sessions a week after warming up before climbing that are very short that are up to 6 hangs if I’m feeling very strong, but as little as 3 hangs.

Since I’m working back into V6 after a very long break and I’m a pretty big guy I will do either sets of half crimp and/or 3 finger drag (at bodyweight) with hangs going up to 10 seconds and up to 3 minute rests before my climbing sessions. Depending on how I feel I will cut that down to just one grip type , preferring 3 finger drag.

For someone who hasn’t been climbing for very long I would honestly recommend getting as much milage as you can and doing sub max or “no hang” as supplemental to help build your tendons up.

Just my 2 cents and your mileage may vary and all that.