Thanks, Tim Schaeps!
Add a new profile (in “Profiles” section of sidebar) → + New empty profile. Settings:
bash.exe (found in the bin folder of your Git for Windows install – don't use git-bash.exe because it will start in a standlone window outside Windows Terminal)
%USERPROFILE%\source\repos)
usr\share\git folder of your Git for Windows install
Save! (Even better, as you go along)
Startup (at top of settings sidebar). Settings:
Save