On $T$-spaces in a relatively free two-generated Lie nilpotent associative algebra of index $4$

In this work, we continue to study $T$-spaces in Lie nilpotent algebras of index $l>3$. The focus is on the two-generated algebra of index $4$, where simple finite systems of generators are specified for a broad class of $T$-spaces in $T^{(3)}/T^{(4)}$.