How to get gromit working without a Pause key?

I have a Wacom tablet. It is a bit old, but it works in Ubuntu. I can use it as a mouse, or in other programs, when I select a tool, I can paint and draw.

What I want to do is "annotate my desktop", for instance, I might have a pdf open. I do not want to annotate the pdf, I want to draw on the screen, over the pdf, underline words, circle phrases, stuff like that. The pdf is untouched.

Actually I want this for classroom use, on our big new "intelligent blackboard" screens. In the classroom I can press a button below the big screen to activate "screen annotate", then I can use my finger to write or circle or draw. I would like to do this using my Wacom tablet, not my finger.

I was given a tip that gromit-mpx can do this in Linux. I installed gromit using apt.

First problem: where is my pause key?? I have no key marked "Pause" on this Samsung 3500EL laptop.

I use ibus input. When I look at the keyboard layout chart and press any and all buttons, Pause, shown on the keyboard layout chart (which looks like a desktop computer keyboard, not a laptop keyboard), does not light up.

Then, in bash I get this error:

pedro@pedro-512ssd:~$ gromit -a Gtk-Message: 12:47:33.019: Failed to load module "overlay-scrollbar" Enabling No. 0x55dcf67fa3a0: "Wacom Bamboo One S Pen stylus" (Type: 1) Enabling No. 0x55dcf67fa130: "ETPS/2 Elantech Touchpad" (Type: 0) Enabling No. 0x55dcf67fa200: "Wacom Bamboo One S Pen eraser" (Type: 2) could not grab Hotkey. Aborting... pedro@pedro-512ssd:~$ gromit --help Gtk-Message: 12:48:08.016: Failed to load module "overlay-scrollbar" Unknown Option for Gromit startup: "--help" Please see the Gromit manpage for the correct usage pedro@pedro-512ssd:~$

I have read the man page and I tried looking at xev, but I'm afraid the output just confuses me.

How best to make gromit work in Ubuntu 18.04 on this laptop?

What key should I try?

Gromit Manpage:

-k , --key will change the key used to grab the mouse. can e.g. be "Pause", "F12", "Control_R" or "Print". To determine the keysym for different keys you can use the xev(1) command. You can spec‐ ify "none" to prevent Gromit from grabbing a key.