I need to consistently show 2 decimals, including when the number is a full integer, or only has 1 decimal. Searching the forum I found references to custom_display_format, but I have no idea how/where to implement it.
For example, here it should be 2.25, 1.00, 2.00 and 1.50:

Alternatively I could use a calculated field, but converting numbers to strings in sql for this purpose would be inefficient (and a lot of extra work and complexity), so I'd like to avoid it.