Under certain circumstances, you may wish to have some additional custom conversions in the style of shims which dovetail into the same implicit prioritization mechanism (e.g. so your custom Monad instance doesn't conflict with the one that shims is trying to automatically materialize). An obvious example of this is the shims-effect subproject, but it's easy to imagine third-party projects which may have similar needs.
This kind of extension can be achieved by mixing in the shims.ShimsCore trait into your top-level conversion import and then explicitly declaring dependencies by mixing in the specific conversion traits as necessary (e.g. shims.conversions.MonadErrorConversions). You can see an example of this in shims-effect:
Mixing ShimsCore into ShimsEffect, which is subsequently extended by the shims.effect package object, is what brings in the entire set of core shims coercions, with appropriate prioritization. Mixing in MonadErrorConversions into TaskInstances ensures that the taskEffect definition has higher priority than the automatically-materialized MonadError instances in shims.