The only way I could see to do that would be to insert the link into an ampscript block. You can use a bug that has caused multiple people tons of issues to your advantage.
Sample question on issue
Article about the issue
Sample code to use below:
SET @FirebaseURL = [YOUR URL]
<a href="%%=v(@FirebaseURL)=%%">Click me</a>
This should have the URL be missed from the click tracking sweep through so it will not redirect and instead be a direct link.
EDIT To do it with domain only, you can set it up with either an ampscript variable or personalization string.
%% [ SET @domain = "http://www.FireBase.com" ]%%
<a href="%%=CONCAT(@domain, '/morestuff')=%%" >Click here </a>
The href should be able to be changed in the editor window through "edit link" or something like that.
<a href="%%firebasedomain%%/morestuff">Click here </a>
The personalization is pulled directly from the data (however you want to set it up) and csn also can be edited in content block ui.
You may need to tweak a bit each time, but in general this should solve your need.
EDIT To ensure link tracking you should wrap the variable with a RedirectTo() function.
<a href="%%=redirectTo(@FirebaseURL)=%%">Click me</a>