How can I get to recovery without Volume Up hardware button?

Or, 'My tablet's hardware "Volume Up" button is broken, now what?' I'm trying to root an Asus TF300TG Transformer tablet (a 2012 model, unlocked) following [this guide on XDA Forum](https://forum.xda-developers.com/showthread.php?t=2617298) : - I have installed the USB drivers on my computer - Rebooted tablet to fastboot - Flashed the TWRP recovery without problems - (Rebooted normally, verified that tablet still works as usual) - Rebooted to fastboot again - Got to the point where I should boot to the new recovery That step requires me to press the Volume Up button to select the recovery option on this screen: In my tablet, however, the button is broken (and has been for some years now). Is there a way to get into recovery without actually pushing it? What I've tried: - Pushing harder - Pushing the other two HW buttons: Volume Down moves the selection, Power does nothing - Connecting the keyboard dock: there is a Volume Up button, but it doesn't do anything in fastboot mode; none of the dock buttons do anything - Connecting a USB keyboard via the dock: no keypresses seem to do anything in fastboot - Rebooting to recovery using fastboot reboot recovery: invalid command - Booting an image using fastboot boot twrp.blob (and various other recovery images from my computer): loaded to tablet, then failed (note the empty error message)

downloading 'boot.img'...
   OKAY [  0.398s]
   booting... FAILED (remote: )

Is there a different way to get to recovery?