The "long term skill shortage list work instructions" can be found in
WR3 of the ops manual. Time spent on a Work Visa granted under any other instructions can not be considered for the purposes of applying for a Resident Visa under the RW4 instructions (as per RW4(a), previously quoted).
Furthermore, you are explicitly asked if you have held a Long Term Skill Shortage List Work Visa for at least 24 months on question I5 on the INZ 1000 form, which is the form you need to fill in to apply for a Resident Visa for a wide range of categories, Residence from Work being one of them. (In fact, this form is used for pretty much every category of Resident Visa that does not involve submitting an Expression of Interest and being invited to apply for residence based on that EOI being selected.) Additionally, the
Self-Assessment Guide for Residence (INZ 1003) explicitly states that, for the Long Term Skill Shortage List Residence Category, you must "have held a work visa granted under the Long Term Skill Shortage List Work Category for at least 24 months".
It should be obvious by now that the time spent employed under your previous Work Visa can not be considered when applying for a Resident Visa under the Residence from Work Category, even if that employment met LTSSL requirements.
If you want to apply for a Resident Visa before you become eligible under the Residence from Work Category, you may want to consider the
Skilled Migrant Category (though, SMC is currently backlogged to hell with seemingly no end in sight, so it may actually turn out to be slower!).