Features such as saving sessions are available in Desktop Environments like KDE, GNOME, Xfce.
There is no such thing in window managers like Openbox.
However, in Mabox there is a solution that I use - powerful but rather for advanced users - called DeskMngr.
Try it - you will find them under middle click on desktop - it allows you to save the list of open windows as sessions and restore them later.
Good command line knowledge is required because the saved file must be adapted to your needs.
A little bit more about it → DeskMngr - save and restore desktop sessions (beta)
Give it a try…
If you think that something like this can be useful to you and you need help, I will be there 