QGIS » QGIS Application

Whilst many Layer settings are accessible from the Layers menu instead of the context menu being needed, some items such as Filter settings are only available from the context menu.

Afaik, there's no feature available ONLY from context menu; they all have duplicate(s), in this case, in View or Layer menu. The filter feature can be found under Layer menu or using ctrl F.
Concerning the issue, i have no opinion as i'm less a Qgis-linux user.

At the moment I am attempting to nail down that this might be a XFCE specific issue, along with a drag and drop problem., Is anyone testing much with XFCE?

My testing leads me to conclude this is application specific rather than a particular desktop environment for Linux.

I'll try to explain what I think the key issues are. If a user can hold the mouse perfectly still while right clicking they have no problem. But if the mosue moves slightly they have a problem because the item on the menu gets selected and somehow clicked. I don't quite know how the click happens, but the select happens.

Whilst maybe when we all used mechanical mice with mousepads, these days most of us use optical mice on slippery desktops or just the fact that they have slippery pads attached to them, hence it is difficult to avoid this small movement when clicking on something. It got really bad when I started using a second computer with its own brand new keyboard and mouse (stacked over the keyboard and mouse of my first computer, so they can be used simultaneously) and the new mouse and desktop were even more slippery than the ones for the first computer)

I think the answer is looking at where the menu is positioned in relation to the current position of the mouse, and whether it can be moved a bit further away.