How to draw arrows in Lichess without beeing annoyed?

On https://www.lichess.org you can draw arrows (only visible for yourself) on the board during the game or during training. You can draw an arrow by holding the mouse button and right click from square A to B. Different colours are achievable when holding Alt (blue), Shift (Red), Alt+Shift (Gold). Here is my problem. Whenever I want to draw a red arrow, I press Shift and draw it, but the right click context menue opens when I release. Is there any way to prevent the context menue from opening?

I'm using Firefox 70.0 16-bit and Ubuntu 18.04.03 LTS.

Edit: Same thing happens on Windows 10 with the newest Firefox.

Lichess allows you to use Ctrl instead of Shift:

• Shift+Left Click or Right Click makes a green arrow
• Alt+Right Click makes a blue arrow
• Shift+Right Click or Ctrl+Right click makes a red arrow
• Shift+Alt+Right Click or Ctrl+Alt+Right Click makes an orange arrow

Incidentally, it seems there is no way in general to prevent firefox from opening a context menu with Shift+Right Click, even as a user setting. See here: https://bugzilla.mozilla.org/show_bug.cgi?id=897379#c4