While our brain is good at storing ideas, it has other things to worry about such as the random thoughts passing by each day, context switching from one task to another, and generating new ideas.
A lot of the newer thoughts have more chance to be gone in a few hours.
For this, you want to make a dedicated repository.
- The important random thoughts and the generated ideas can then be revisited for future ideas.
- Tasks can then be tracked, reminding what and/or when to be done.
If you want to store an idea for an indefinite future (e.g., a project idea, future hobbies) that you cannot surely do now, you can then create a dedicated inbox.