This issue is about the Persistent List View experiment (#28637), currently only available in the Site Editor.

Currently, Navigation, Inserter, and List View sidebars are alternative between each others: opening one will close the other.

Given the Persistent List View is supposed to be persistent, we might want to find a better interaction between the three sidebars.

Possible solutions:

1. Remember if the List View was open when opening another sidebar, so that closing that will automatically reopen the List View.
2. Keep the List View open besides one of the other sidebars (Inserter and Navigation will remain alternative between each other).
3. Split horizontally the secondary sidebar, so that Inserter and List View can be open at the same time, occupying half (or a resizeable portion) of the sidebar slot.