You can edit your data grf (or create a custom one) with this path folder: data\luafiles514\lua files\skilleffectinfo\
If you don't have this file, it can be downloaded from: https://github.com/zackdreaver/ROenglishRE
Inside, edit effectid.lub
EF_FIREPILLARBOMB = 97,
EF_DETECTING = 119,
EF_TWOHANDQUICKEN = 130, <--Add this line
EF_ICECRASH = 135,
EF_BRANDISH2 = 144,
Then skilleffectinfolist.lub, add the following lines at the end:
},
[SKID.KN_TWOHANDQUICKEN] = {
beginMotionType = ACTOR_STATE.ST_SKILL,
effectNum = 1,
effectID = { EFID.EF_TWOHANDQUICKEN }
}
(Add a coma to the previous closing bracket and the last line must not have a comma)
Can't confirm if it completely works as you need to.