does anyone know 'how use_skill', 'timeline', 'add_eft' work? also those position varaiables...

I'm trying to create a skill tree, with passives that can trigger from on hit effect.
Here are some scanerio/cases I would like to implement:
[passive A - toggle on an active skill if character land a crit hit]
[skill B - cast another existing skill]
[skill C - allow additional effects to skill B]
etc.

It seems like add_eft and timeline is different to skill cmd...

I've been reading the official mod guide and testing with the mod/skill editor but nothing seems working.

any help would be appreciated.