what do you mean by "check the casing"? Sorry I am new to extensions, could you tell me where I click in Qlik Sense to see the casing?
1. I created a new extension
2. I completed the qext and the js file
3. I clicked the + sign on the right to create a new page
4. I typed title.css for the new css file
5. I looked for the new tab to edit the new css file
6. there was no tab - so I thought I made a mistake
7. I tried to create the page again, and Qlik let me know it existed already.
Normally the .css page would show up as the last tab in the extension ribbon.
Yes, that's right it has to show up. The best way to check is by going to the extesnion folder location and checking it there. C:\Users\sangramr\Documents\Qlik\Sense\Extensions\<Ext name> -- check the name of the css file here. If you delete the css file here , you will be able to recreate it from the dev-hub.
Also make sure that the file name you use exactly matches as its case sensitive.