How properly modify a javascript code or extend a controller in UI5 time approval application

Hello Experts,

We want to disable mass approval in Time Sheets in HR Renewal application:

I have located application, controller, view, script, I think I know what needs to be modified, but I am not sure how to proceed.

For Fiori, there is a nice blog, How to extend a SAPUI5 Fiori application (both view and controller),

which tells the steps...

For example, I do not know if I need to install IDE, create an extension project and so on... or it is possible to create a custom controller js file or even modify the original htmssCATSApproval.js.

Is there any documentation/blog that tells exactly what to do?  Any action I try to do results in pop-up requesting the Access key.

Thank you very much in advance,

Inna