Thanks to Windows Terminal being open source, we can directly look up the available commands in the Windows Terminal's code! I took the liberty to list them for you here:
adjustFontSize
closeOtherTabs
closePane
closeTab
closeTabsAfter
closeWindow
copy
duplicateTab
wt
find
moveFocus
newTab
nextTab
openNewTabDropdown
openSettings
openTabColorPicker
paste
prevTab
renameTab
openTabRenamer
resetFontSize
resizePane
scrollDown
scrollDownPage
scrollUp
scrollUpPage
scrollToTop
scrollToBottom
sendInput
setColorScheme
setTabColor
splitPane
switchToTab
tabSearch
toggleAlwaysOnTop
commandPalette
toggleFocusMode
toggleFullscreen
togglePaneZoom
toggleRetroEffect
toggleShaderEffects
moveTab
breakIntoDebugger
findMatch
toggleReadOnlyMode
newWindow
identifyWindow
identifyWindows
renameWindow
openWindowRenamer
action
Note that the file also lists the command unbound, but this is a placeholder used to remove keybindings. There does appear to be a few commands here that aren't listed in the documentation. One of which is identifyWindow which displays the name and ID of the current window in a tooltip.