Reproduction guide:

• 1. create two workspaces
• 2. in workspace 1, evaluate this code: (e.g. by using M-:)

(setq mywin (display-buffer (get-buffer-create "buff1") '(display-buffer-in-side-window (side . left) (slot . 0))))

buff1 is displayed on the left in a side window.

• 3. evaluate this code: (window-parameter mywin 'window-side)
     returned value: left
• 4. switch to workspace 2, then switch back to workspace 1
• 5. evaluate this code: (window-parameter mywin 'window-side)
     returned value: nil, meaning buff1's window is a normal window now, not a side window.
     My expectation is that buff1's window should remain a side window.

To be fair, the same result happens if I replace step 4 with this step:

• M-: (window-state-put (window-state-get mywin t) mywin)

Changing the value of window-persistent-parameters before step 4 solves my issue:

(add-to-list 'window-persistent-parameters '(window-side . writable))
(add-to-list 'window-persistent-parameters '(window-slot . writable))

I'm not sure why window-side and window-slot are not persistent by default, there could be a reason I'm not aware of.

I'm mentioning all this because I thought it could be helpful if eyebrowse modified window-persistent-parameters accordingly or suggested it as user configuration in the readme.