Just wanted to say I’d also like this, with the use-case being a command which computes results to be show in the sidebar.
If a user invokes the command without the sidebar already open, the only way to alert that the command actually worked is to throw up a result asking them to open the sidebar.
I’d like this too. I have keyboard shortcuts for many of the built-in sidebars, but third-party sidebars are less useful without a way to get to them quickly.