Just what I've been expecting (in one way or another).
First off, not that it matters, but I've got no idea how you managed to get "Debug" in your Safari menu bar, or how you got rid of "Notifications."
And here's how I believe you can get "Debug" back where you want it in STP:
Make your Date & Time icon considerably smaller by editing the info it displays in System Prefs > Date & Time or with a 3rd party app. (Do you really need to show the month and AM/PM?)
Make your battery icon considerably smaller by editing the info it displays (control-click on the icon) or with a third party app. (Couldn't you live without battery %, i.e. by eye?)
By way of comparison,
here's what my icons look like. (Date & Time is Itsycal [Donationware]:
http://www.macupdate.com/app/mac/49674/itsycal, and Battery is SlimBatteryMonitor [Donationware]:
https://www.orange-carb.org/SBM.)
And as you think this through, remember that Apple has increased the space between icons by a considerable amount (too much, in my opinion) in Big Sur, so you'll need to deal with this stuff later, if not now.
Bottom line, though, is that Apple should have realized that "Safari Technology Preview" takes up
waaay too much menu bar space and offered an alternative option. (Also, the amount of space that Apple's battery icon takes up has been an ongoing evoker of complaints for - more or less - ever.)
Oops! Crossed with Ira.
