Never close current solution when opening another

Hi all,

I occasionally will want to have multiple solutions open in Rider. For example, the main solution for my Unity project, plus another solution for a library DLL, etc.

I have been able to get two Rider windows open once or twice - but never figured out how to do it reliably. Yet, in IntelliJ I can do this all the time and regularly do (e.g., have multiple Cursive Clojure projects open at once).

In Rider, if I click File -> Open -> (a previously opened project) it always closes my current project.

Please, would someone tell me how to disable closing of the current project, or at least how to open another project/solution in a new window without closing the current one, or at least add a pop-up that says "Do you want to open this in a new window or replace the current window" like IntelliJ used to do (and probably still does but I haven't seen it in a while).

Thanks!