In Opera 69.0.3686.0 after enable flag opera://flags/#workspaces-sidebar-context-menu I have context menu but... but in my opinion these options are of little use ... For example, in my opinion, buttons from worspace should have options as I wrote in the proposal (mute / unmute sounds from all cards in a given context, save all cards for quick selection and close all cards) ). Meanwhile, I have:
hide [name workspace]
edit [name workspace]
manage workspaces...
hide sidebar
sidebar setup
For me, these options are pointless because:
I can hide worskpace from the "..." button
editing workspace - as above
manage workspaces - as above
hide sidebar from the options in the "..." button and in Easy setup
sidebar setup - after all, it is equivalent to clicking on the "button... "at the bottom of the sidebar.
These options in the context menu are totally pointless, only replicating the options to which "close to the cursor" is already available.
The context menu in the sidebar can be a useful function. But only if add useful(!) options there.