Replace WBS Code

Is it possible to switch off the WBS code, and display an integer for the task Id, that is also displayed in the Predecessor and Successor columns.
The WBS code gets too long for nested tasks.

Hello,
If you only want to show the task ID instead of the WBS code, you can easily do that by adding a column with the id name. Or you can use the template function and return the task.id parameter:
https://docs.dhtmlx.com/gantt/api__gantt_columns_config.html
https://docs.dhtmlx.com/gantt/desktop__specifying_columns.html#datamappingandtemplates

Here are examples:
http://snippet.dhtmlx.com/5/11731dc5a
http://snippet.dhtmlx.com/5/bee3d8f29

But if you want to use the task ID when editing the predecessors in the inline editor, there is no built-in way for that. You will need to implement a custom solution. The easiest way would be to modify the values when you open and close the inline editor. Another way is to add a custom inline editor and implement the logic for creating and updating links.
I have the following example that can help you to start:
https://snippet.dhtmlx.com/5/e1182da76