So on the trial version, you are not allowed to save. I know this because I have the trial version and if anybody is on the trial version another way to save a draw is using the snipping tool and selecting your drawing and then when you come back it should be in your recent. The mods are likely not going to switch it so this Is the only way I know of.
Actually there is an even easier method that is:
- Selecting the whole canvas (Ctrl+A or ⌘A)
- Copying its content (Ctrl+C or ⌘C)
- And pasting the result in other program/the full version of Aseprite (Ctrl+V or ⌘V)