There are no default transformations in the EPSG Geodetic Parameter Registry. Sometimes you can use the remarks and or the accuracy value to determine which is the currently accepted transformation as defined by the government or the most accurate transformation.
For instance, in Belgium, there are two transformations between BD72 and ETRS89: 1652 and 15928. The accuracy of the first is 1.0 m while the second is 0.2 m.
You also have to check the area of use, because you may find a very accurate transformation, but it has a limited area of use. In your example for EPSG:4230, EPSG:1133, ED50 to WGS 84 (1) has the largest area of use, and one of the larger accuracy values.
I decided to check 4267 (NAD27) on epsg.io because it has no clear option for a default transformation. As I suspected, it doesn't have one.
Note: epsg.io has no connection to the official EPSG Geodetic Parameter Registry.
Disclosure: I'm on the Geodesy subcommittee that maintains the EPSG Geodetic Parameter Registry.