I have a directory with lots of small zip files (40000+) in it. When I select all files and right click to get the context menu there is a warning about the number of files and then a delay of around 1 minute before the context menu appears. I've increased the number of files before the warning message appears but the delay is still there. The delay is so long it makes using the context menu in opus unusable for this directory and I have to use explorer in which the context menu appears immediately or keyboard shortcuts for cut/paste operations involving large numbers of files.
40,000 zip files is going to take a long time for the context menu to build (especially if any context menu or Opus itself are inspecting the files, which might cause them all to be virus scanned).
Most actions can be done without opening the context menu, via the toolbars, if that helps. It depends what the action is, of course, but there's probably an instant way of doing it. What is it you're aiming to do with them?
At the moment I'm moving the files around and splitting them into smaller subdirectories. I can use CTRL+C keyboard shortcut to copy large groups of selected files but using the context menu would be preferable as it could all be done without any keyboard input.
If you open the destination folder in the second file display, you can move all selected items into it by clicking the Move button on the toolbar. That's much faster than using a context menu (and faster than cut & paste in general) and doesn't involve the keyboard.