Set your shell prompt to a sequence that outputs multiple lines, then moves the cursor back up the same amount of lines. Both Conhost and Windows Terminal support the 'ANSI' or 'ECMA' terminal control codes now.
set PROMPT=$_$_$_$_$_$e[5A$P$G
$_ outputs a newline, $e[5A moves the cursor five lines up.
The Bash equivalent is PS1='\n\n\n\n\n\e[5A\u@\h \w\$ '.
does Windows Terminal support "scroll past bottom" like classic [conhost]
I couldn't find any setting to allow that.
If not, is this a known design limitation of Windows Terminal?
Conhost and the Windows Console API was designed for a fixed-size 'display' buffer. If it's 300 lines tall then it's 300 lines tall (meaning that – from what I remember – you stop being able to scroll past the bottom if you fill up those 300 lines).
Windows Terminal was created as part of Microsoft's effort to switch away from the Console API and towards the Unix-style "tty" API. Due to their roots in a paper-based teletype (versus a fixed-size CRT), Unix-style terminals are more stream-oriented, and the dynamically-growing scrollback in terminal emulators kind of reflects that. Most terminal emulators don't support forward scrolling (unless they implement 'jump scroll').