Maybe I'm hallucinating...
But I was sure that in an older version of BTT we could customize the BTT menu bar icon.
Give it a personalized icon or have it invisible...
But in my current version, 3.952, although I know that I can add an action called "Custom Menubar Icons", I can't for the life of me figure out how to customize the icon in the end... Help please 
If you don't mean the notch bar, then probably the icons at "other triggers" (cmd+9)
You can copy/paste the icon. Not sure if that answers your question.
Thank you for the reply!
I found the action you showed to me and I add a (preset) icon, like you, but after that I'm lost.
Just to be clear, I want to change the BTT menubar icon into something like a spacer or line.
I mean the standard BTT config icon in the screenshot.
Ah, the BTT icon, sorry I don't know that. I didn't even know you could change that.
customizing the BTT menubar icon has never been possible (although, it’s maybe a good idea). However you can hide it in the BTT settings!
Oh so I was right... I HAVE been hallucinating!
Sorry about that! (Doesn't help that I have a bad flu, maybe I have fever dreams)
I had this strong idea in my head that I could set a custom icon and just have it be a spacer, separating my default MacOS menu bar items from the personalized ones, for quicker and better visual organization.
Click the spacer, boom, BTT drop down config menu.
...
Maybe I had a dream about it, but maybe it gives you ideas about implementing it 
Sorry for the confusion again!
Still not sure if I understand this correctly. If you want to open the settings, you can use the predefined action.... and get well soon
I mean you can hide the BTT icon and then create a new custom icon in the „Automations, Named & Other Triggers“ section. If you the assign the context menu action you can create your own drop down menu