The thing is with admin templates is they only exist in the master style and, as such, any changes to them would be wiped out and have to be reapplied after each upgrade.
This is why we essentially hide them behind development mode because editing admin templates (such as those which belong to other add-ons) is a development tool and not a tool for admins to change things.
There isn’t a direct way to enable debug or development mode on Cloud but we can enable it for you and disable it when you’re finished but, once again, this is not something we recommend for admin templates and we would actively discourage that.
The best way to change the appearance of admin templates is to use an add-on.
These would persist through updates and with the template modification system do not require editing templates directly.
Template modifications are great (TMS).. but they ARE somewhat problematic to use as it appears that you have to have development mode enabled.. which to me is somewhat an oxymoron if so... especially in the cloud environment. I really don't see see why XF currently forces you to use development mode for TMS edits... it's not like it's much different than editing the actual templates in use. I personally see it as a "weakness" in the system, especially when it comes to their cloud offering. At least with the self-hosted you can change a few config.php entries and enable it... but if I remember correctly (and I have slept SEVERAL times since then) in the v1.x version of XF it was enabled without doing such.