This issue has two levels. I'll start with the easiest to fix...
1) Recipes to craft normal arrows and bolts do not exist at all on the Dungeon Maker merchants (both default ones and custom merchants). Even with current mods, we cannot just add them as far as I know.
* Suggestion 1 : add those recipes (that level 1 characters get) to DM merchants.
2) All memory of recipes are zapped 100% when characters end/start any DM adventure.
* Suggestion 2 : I know it is a whole function to program, but saving recipes to character "Update" (with the character sheet) when they exit DM adventures.
I made a "Hearquarters" campaign/mod (to sell loot and buy gear and craft), where I grab recipes and carry them before starting a DM campaign (I read them though ONLY once I am inside the DM campaign, otherwise my characters would forget all recipes instantly). BUT I utterly cannot craft arrows/bolts, as the recipes cannot be bought at all nor placed in a container.
I can circumvent the issue partly by buying arrows and bolts instead of crafting them, but that is a bit sad.
It is an oversight.
* Suggestion 3 : though ideally would be cool if characters just always knew the basic recipes without needing recipes, like crafting arrows/bolts (Smithing), basic healing potions (Herbalism), basic poison (Poisoner) and Scribing the level 1 spells you know, etc. I also wonder if it would not be better for characters/players to simply see all recipes, as they still need to find/buy the ingredients and craft.
Steam profile : https://steamcommunity.com/id/baraz/