A custom value of a feature is a unique value for the product concerned. It can not be shared with other products. The interest is that if it is deleted, it is not suppressed in other products.
The first thing to do is to display and select the product, then display its features in the tab of the same name.
The "Custom" features can be identified by the check mark in the "Custom" column, to the right on the same line.
To change a value, click it:
The selection or editing window opens. If the value is customized, its various translations appear in the small table of this window. Click the line of one of the languages to change the value:
Do this for each language and validate:
You're done :
Note that in the same way you can replace the personal value with a standard feature value (shared with other products) by selecting it in the 1st drop-down list at the top of the selection and editing window.
However, note that this window does not allow you to modify the text of a standard value. This can only be done in the lower part of the tab (the four small tables at the bottom)
Category's other articles Gestion en masse des caractéristiques PrestaShop