this problem can be solved without editing webix.global.d.ts
to override global definitions, you need to create own definitions
webix.override.d.ts
declare namespace webix {
function ajax(): webix.Ajax;
function ajax(url: string, params?: any): Promise<any>;
}
this is required for forward compatibility.
to not edit global definitions after each update.
the main problem is that new file must be loaded after global one.
if they are in the same folder, then no problem, as alphabetically new file is coming after global one.
in other case, you should check locations, to make sure that overrides loaded after global definitions.