You can customize column titles, in most kanban views, using Dolibarr's standard mechanism for editing translations:
Go to Home> Configuration> Translation> Find a translation
Select the language (en_US for example) and enter the label you want to modify in the search line, column "Current translation" and click on the magnifying glass.
In the rows of the results that appear, locate the one that corresponds exactly to the search label then click on the "+" icon to modify it.