endless mode is missing all the interesting story events, but it's a signal based event, so maybe its possible to get
you can simply keep playing your story mode save for endless though if you think nothing else will happen in it, there's just no more scripted events
Viewing post in Gravity gun in endless mode
Initially, I had a save in story mode, and the cannon was there, but the day counter stopped at day 49. This annoyed me, so I decided to move to the infinite along with all my things. then one of two things: either I’m a fool, or the game is bugged, but in the end my things from the mailbox simply disappeared, along with the gravity gun. Now I’m wondering whether I need to create a new save in the story save and wait for this signal or whether it will appear in the endless one.
I would spawn things in in a sandbox save, then convert it to a normal save and use the mailbox
DO NOT convert your normal story mode save to sandbox because a few things get deleted permanently for some reason (like maxwell and some of the argemia plushies)
to change a save's gamemode go to votv's save directory (appdata>local>votv>saved>savegames) and change the prefixes of your saves to match the mode you want them in (a_ambient, s_story, b_sanbox, and I'm pretty sure i_ is endless and l_ is solar)