SUNTF[{a}, i, j] is the SU(N) T^a generator in the fundamental representation. The fundamental indices are explicit.
Overview, SUNFindex, SUNT, SUNSimplify.
SUNTF[a, i, j]T_{ij}^a
SUNTF[{a, b}, i, j]\left(T^aT^b\right){}_{ij}
SUNTF are c-numbers, hence they are commutative objects and do not require a dot
SUNTF[{a, b}, i, j] SUNTF[{c, d}, j, k]\left(T^aT^b\right){}_{ij} \left(T^cT^d\right){}_{jk}
SUNTF[{a, b}, i, j] SUNTF[{c, d}, j, k] // SUNSimplify\left(T^aT^bT^cT^d\right){}_{ik}
A chain with closed indices is automatically converted into a trace
SUNTF[{a, b}, i, j] SUNTF[{c, d}, j, i] // SUNSimplify\text{tr}\left(T^a.T^b.T^c.T^d\right)
SUNDelta[a, b] SUNTF[{a, b}, i, j] SUNTF[{c, d}, j, i] // SUNSimplify\frac{1}{2} C_F \delta ^{cd}
SUNTF[{a, b}, i, j] // FCI // StandardForm
(*SUNTF[{SUNIndex[a], SUNIndex[b]}, SUNFIndex[i], SUNFIndex[j]]*)