Technician reported failure to follow procedures during a multiple shift A Check resulted in not reactivating the Leading Edge Slats.

Narrative

I work midnight shift ZZZ and was assigned Aircraft X; a B777 A check aircraft with multiple Job cards. This Aircraft was a multiple shift aircraft. When we started at XA PM the plane was already in the hangar with some task cards opened. There are different work packages which sometimes ask for redundant procedures.Leading edge slat lubrication has a job card to lock out the Slat Electric Motor power on P200 panel. This card was probably started on the previous shift they used the 'on board' We are frustrated with our paperwork and I probably should of checked for the collar removal; but again assumed other task card should of covered the re-activation. LOTO kit from the flight deck. To prevent personal injury the Leading Edge must be locked out.Both engine work cards would require LOTO of the Leading Edge so as to not damage engine fan cowl. (but mostly the GE engines as the Pratts are not interference fit!)The C/B in question is located forward of the E and E door right tunnel. (access is restricted by the design of the aircraft structure so the Circuit Breakers are not readily visible or accessible in this area) So when we started our shift the systems where locked out. The type of LOTO flight deck kit is not of a numbered type as is the E LOTO board system.I was working by myself on the #2 engine; wiring inspection; filter replacement; etc. At the end of our shift we finished task assignments Close up of engine cowls; reset systems; remove stands; get the plane ready to push out of hangar.We have explained to our management team the convoluted quagmire of 'A' check paperwork. The paper package is a synopsis of a four day 'C' check. To the best of my recollection I did sign for the re-activation of the electric motor slats; but I did not physically re-activate the system. Techs know other task cards have redundant procedures and a tasked could be accomplished from those cards.