The tent's storage has limited space in the beginning, but can be upgraded by speaking to Flamey and spending coins.
You can also increase the storage space of your backpack by talking to Mr. Kit and purchasing a backpack upgrade. Please note that you may need to upgrade Mr. Kit's catalog of items for the backpack upgrade to appear.
Mr. Kit also sells a decoration called "Chest". Upon placing it, it can be used to store items similar to how your tent's storage works.
Leaving items on the ground We don't recommend leaving any of your items on the ground as it is not safe and it may cause the item to disappear. This may also cause some items, shells are a good example, from spawning new ones. Decorations or pets are not affected though and will not disappear. They'll stay where you put them.