That’s correct, the delete button is only displayed when we have specifically set that button to the editing logic of that specific column. Can you tell me on what type of column the button is missing? We can have a look if we can add it or you could have a look at adding the button yourself with the following hook:

https://github.com/codepress/admin-columns-hooks/blob/master/acp-editing-view_settings.php

I’ve added an example that adds the clear button to every column. You probably don’t want this for every column so my advice is to check for specific column types only. There are some columns where you don’t want to unset a value, like for example, removing the value for a post_status will probably give some weird unexpected results.