Approaches (on this site) refer to an integrated package of methods and processes.
For example, 'Randomized Controlled Trials' (RCTs) use a combination of the methods random sampling, control group and standardised indicators and measures.
Evaluation approaches have often been developed to address specific evaluation questions or challenges. For example, the Contribution Analysis approach has been developed to address questions about the feasibility of concluding that an intervention has contributed to an outcome in circumstances where a direct causal relationship is difficult to demonstrate.
If you're looking for an approach that's not listed here, it could exist as an evaluation method. If you still can't find it, get in touch.