Please read :

Also, in table 9-37, we should fill binIdx 3 and 4 with na for ref_idx_l0 and ref_idx_l1.

maxBinIdxCtx equal to 0 is correct for sao_type_idx_luma, sao_type_idx_chroma and merge_idx because the bin with index 0 is the last bin that is coded using context derivation. All bins with binIdx > 0 are bypass coded.

For which Syntax Element should we fill binIdx 3 and 4 with na?

For sao_type_idx_luma and sao_type_idx_chroma, if we apply the text as it is :

From 9.3.2, bypassFlag will be not defined for binIdx = 1 because a value is assigned to ctxIdxOffset for this syntax element (so the first entry of bypassFlag is not applied) and maxBinIdxCtx = 0 (so the second entry of bypassFlag is not applied).

If bypassFlag is not defined, the decoding process flow cannot be applied as it uses bypassFlag to determine context or bypass decoding should be used for a given bin.

My suggestion is :

In 9.3.2, we add a case for bins with binIdx > maxBinIdxCtx :

Otherwise, for each possible value of binIdx up to the specified value of maxBinIdxCtx given in Table 9-32, a specific value of the variable ctxIdx is further specified in subclause 9.3.3. In such a case, bypassFlag is set equal to 0. For binIdx greater than maxBinIdxCtx, bypassFlag is set equal to 1.

Then for Table 9-32, some of the values for maxBinIdxCtx need to be modified :
+ part_mode : maxBinIdxCtx should be 2
+ cu_qp_delta_abs : maxBinIdxCtx should be 4
+ ref_idx_l* : maxBinIdxCtx should be 1

The CABAC part was cleaned up including removing a lot of redundancies in the aforementioned tables. Please check whether everything is ok in the current version v23.