I have a "paintings" custom post type. I created two custom fields: "Custom Small Dimensions" and "Custom Large Dimensions". They are text fields. I only want the fields to show if they are populated. I added a conditional block with the settings shown in my attachment. I added a fields and text block to the conditional block and added the following: <p>Custom Small Dimensions: [types field='custom-small-dimensions'][/types]</p>
I tried this with a painting where the Custom Small Dimensions has data in it but the field won't show up.
Here is the painting: hidden link
Now, for not empty values, once you set the condition for empty value then you should enable the "NOT" button available just under "AND | OR" buttons and save your conditions.