I apologize if I'm blind and missed this. Is this in 4.x? (Edit template code + Compare Differences, Revert, Variables...) Or, was it removed as well? 

I see Designer's Mode, and you can edit skin data directly in the server's folder. I guess this replaced all the tools shown below? 

After you upgrade to 4.x. And then another version of 4.x is released with a revised template--is there a Template Merge Center like there was in 3.x? How do you manage differences?

 

Edited June 17, 201510 yr by Josh Bond

I apologize if I'm blind and missed this. Is this in 4.x?

Customization → Theme → [Your Theme] → Button “Edit HTML & CSS”

Yes, my blindess is now confirmed. Thank you! That's such a relief the editors are still in IPB.

I'm assuming the Template Merge Center went away.

Edited June 17, 201510 yr by Josh Bond

You can check theme differences here: 

http://community.invisionpower.com/index.php?app=core&module=system&controller=plugins&do=diff